Here is an excellent book on these topics:
ON TROTSKYISM
Problems of theory and history
by Kostas Mavrakis
http://www.marx2mao.org/Other/OT73NB.html
On the specific question of "socialism in one country"
Clearly Lenin had hoped for revolution in Germany, and knew that the progress in Russia would be more rapid and sure if the proletariat controled several countries (not just one) -- but as it became clear that the German revolution was not coming Lenin (and the leninists like Stalin) saw they would have to build socialism on their own.
One of the quotes you are looking for Elijah may be this one (on Mavrakis p. 26):
Lenin also said (in the article 'On Co-operation' dictated on 4 January 1923, shortly before his death):
"Indeed the power of the State over all the large-scale means of production, political power in the hands of the proletariat, the alliance of the proletariat with many millions of the small and very small peasants, the assured proletarian leadership of the peasantry etc - is this not all that is necessary to build a complete socialist society . . . out of co-operatives, out of co-operatives alone, which we formerly ridiculed as huckstering and which from a certain aspect we have the right to treat as such now, under NEP? Is this not all that is necessary to build a complete socialist society? It is still not the building of socialist society but it is all that is necessary and sufficient for it."
Trotskyism defines socialism as a world system -- and then (uising circular logic) announces that it can't happen in one country. In fact, communism (the ultimate classless society) can only be reached on a world scale, but the approach to communism, and the early sprouts of communist society (which are called socialism) can (and must!) be built wherever the proletarian revolution wins.
Lenin (also in "Co-operation"
defined socialism in exactly this way (and not in the rigid all-or-nothing Trot
dogmatic way):''Given social ownership of the means of production, given the class victory of the proletariat over the bourgeoisie, the system of civilized co-operators is the system of socialism.''
The construction of socialism is not the same as the "final victory of socialism" (which can only mean worldwide communism.)
At the height of the Cultural Revolution, the Maoists stressed this, and Mao made a major statement on this point in October 1968:
Chairman Mao pointed out in his talk in October 1968:
"We have won great victory. But the defeated class will still struggle. These people are still around and this class still exists. Therefore, we cannot speak of final victory. Not even for decades. We must not lose our vigilance. According to the Leninist viewpoint, the final victory of a socialist country not only requires the efforts of the proletariat and the broad masses of the people at home, but also involves the victory of the world revolution and the abolition of the system of exploitation of man by man over the whole globe, upon which all mankind will be emancipated. Therefore, it is wrong to speak lightly of the final victory of the revolution in our country; it runs counter to Leninism and does not conform to facts."
This is also an important statement of internatonalism -- because it clearly situates the "final victory of the revolution in our country" (even a country as large as china) in the victory of the world revolution.