These questions are hard and require a lot of thought and study to come to the correct understanding. 

Knowledge and growth are very interesting and in depth subjects.  We must continue to grow all of our lives towards the standard, which Christ has set for us. 

EPH 4 V 13

Till we all come in the unity of the faith, and of the knowledge of the Son of God, unto a perfect man, unto the measure of the stature of the fulness of Christ:

We have not spoken a great deal about the foundational subjects of our calling, like, love, faith, mercy and the principals of Christian living.  This is because we have learned them from the very beginning of our calling and we have sat in church and heard many great sermons on these subjects, since that time.  Hopefully we have listened to those sermons and applied them to our lives. 

JAM 1 V 22

But be ye doers of the word, and not hearers only, deceiving your own selves.

Now is the time to build on that solid foundation of Christian living and press on to knowledge of eternal life. 

There is knowledge, which is required for eternal life and we must know what it is and we must have an understanding of it. 

JOHN 17 V 3

And this is life eternal, that they might know thee the only true God, and Jesus Christ, whom thou hast sent

WE MUST KNOW THE ONLY TRUE GOD AND JESUS CHRIST.

That is not my idea, or a nice little bed time story, I am not dreaming this up, this is what God says, not us, it is that simple, we must know God the Father and Christ , eternal life depends on that knowledge. 

Now on to the questions; which I asked at the beginning of the article. 

Is knowledge correct for a certain era of Gods church, and yet not for another? 

Lets look at some examples, we have been in Gods church for many years, we were baptised in 1979, we have been in Gods church for a few years.  During that time we were happy to keep the Passover when the church kept it.  We thought that was correct and we never doubted.  I am sure that  you were happy to keep the Passover the same as we did, and never thought it was wrong. 
In 1999 Jim discovered that the Passover should be kept the following night, when the church keeps the night to be much remembered, we now keep the Passover on the start of the 15th at the beginning of the 1st Day of Unleavened Bread, just after sunset at the start of the holy day.  This is the correct day for the Passover.  DOES THAT MEAN THAT MR. ARMSTRONG HAD IT WRONG? 
No.  For that time,for that era of the church,  that knowledge was not given.  This is extremely important to understand this, brethren. 
Up until we accept the knowledge of the Passover, we are still keeping the Old Testament Passover, we didn’t sacrifice a lamb, because we accept Christ’s sacrifice, but we had not accepted the knowledge of eternal life and crossed the Jordan River we were still in the wilderness.  Until we accept the knowledge of eternal life, we have not crossed the Jordan river.  Therefore the knowledge we learned in the Phildelphia church was correct for us and accepted by us, it is not until we learn the new knowledge of eternal life, and accept  that  knowledge, that God shows us the end time truths which will be revealed and accepted in the end time, by Gods people, who will be in the Laodicean church era.. 

ACTS 2 V 16-17

But this is that which was spoken by the prophet Joel;
And it shall come to pass in the last days, saith God, I will pour out of my Spirit upon all flesh: and your sons and your daughters shall prophesy, and your young men shall see visions, and your old men shall dream dreams:

This happened in the times of the starting of the church, it was correct knowledge for that time, but it will happen in the future and will have a different understanding and meaning for the future. 

So when the church was starting, that prophesy in Joel was right for them, they were not wrong about it, but it will have a different understanding in the future when sons and daughters will prophesy in the future. 

Does God the Father want His people to grow in knowledge of Him and Christ 

Of course He does, look at the following scriptures 

HOS 6 V 6

For I desired mercy, and not sacrifice; and the knowledge of God more than burnt offerings.

ROM 15 V 14

And I myself also am persuaded of you, my brethren, that ye also are full of goodness, filled with all knowledge, able also to admonish one another.

2 PETER 3 V 18

But grow in grace, and in the knowledge of our Lord and Saviour Jesus Christ. To him be glory both now and for ever. Amen.

It is very important that we continue to grow in knowledge of our Father and Christ. 

Did Moses have greater understanding than Abraham. 

This is interesting, brethren.  We know that both Abraham and Moses will hold extremely high positions in Gods kingdom.  Their records are in the bible for us all to read and study into, they were both fabulous men in Gods eyes.  Abraham The father of the faithful, and Moses led the Israelites out of Egypt, and led them for 40 years in the wilderness.  They both were bible greats, spiritual giants. 

However, what I am saying to you  was the same for them as it is for us today.  What Abraham knew was right for him at that time, and yet in Moses time, God gave him knowledge that Abraham did not have. 

Do you find that hard to believe brethren. 

As I have said, both these men are spiritual giants, whether or not they had certain knowledge is not dependent on their greatness or righteousness.  It depends on what time they lived in.  What era the church was in.  Moses had  knowledge, which Abraham did not have. 
Both men were right in their time. 
If we have knowledge that Mr. Armstrong did not have, that does not make us better than he was, that does not make him wrong in what he taught.  Mr. Armstrong laboured faithfully for 56 years in Gods service.  I doubt any of us could match that time or his spiritual record.  We are not better than any of Gods people, it is just that we are living in the end time and God has given us knowledge for this particular time we are in right now. 
Please understand that we are not trying to put Mr. Armstrong down in any way at all, what he taught was right for that era of the church.  Now we grow from there and build on that knowledge and God gives us new knowledge, it is right for us now. 
This is the end time church. 

Now back to Abraham and Moses, as I stated previously; Moses had knowledge that Abraham did not have…….what was that knowledge? 

Lets notice the following scripture 

EX 6 V 3

And I appeared unto Abraham, unto Isaac, and unto Jacob, by the name of God Almighty, but by my name JEHOVAH was I not known to them.

So what is the difference between God Almighty and Jehovah. 

God Almighty means God, there is no doubt about that, however it is a general term, and does not distinguish him as the One True God. But Jehovah is different because it means the One True God. It only refers to the one God who has inhabited eternity. This means that Moses knew that God the Father was the one true God. 

Why did God show this to Moses and not Abraham, not because of righteousness, but because Moses was going to lead the Israelites out of Egypt, God the Father Himself was going to give them the 10 commandments and make a covenant with them. 
This knowledge was required because of the time Gods people were at.  This knowledge was not required to be known, by Gods people in Abrahams time. 

Notice this scripture: 

LUKE 24 V 27

And beginning at Moses and all the prophets, he expounded unto them in all the scriptures the things concerning himself.

Did you notice that, Christ said beginning at Moses, scriptures concerning himself.  Christ said that is when the truth of who Christ is; was  first stated.  That is where we begin to learn about the Father and Christ. 

Now we are living in the last days, we are being given end time knowledge because that is the time we are in right now.  Lets make these things clear and understand them. 

Lets realise that God gives the understanding of the scripture.  We cannot understanding anything unless God opens our eyes to see and our ears to hear. God is the one who will show us new understanding of the scriptures, there just is no other way.

The bible is a living book, it can say something for one group of Gods people in a certain time period, and that knowledge will be correct for those people in that time.  However as time goes on, God reveals extra knowledge to His people. 
This knowledge may be different from what Gods people have known before, however it will be right for Gods people at that time.  It does not mean that the previous understanding was wrong, it simply means they did not have knowledge that was not for their time frame. 

We are now receiving the knowledge which God calls the knowledge of the truth.  This is the knowledge which will bind Christs church in these last days and this knowledge will eventually fill the entire earth. 

There will be one church and one shepherd. 

JOHN 10 V 16

And other sheep I have, which are not of this fold: them also I must bring, and they shall hear my voice; and there shall be one fold, and one shepherd.
 

The bible is a living book. Living and waiting to be understood by Gods people as He reveales it to them.