(1) is anybody familiar with the incremental export/import functionality? If
so, how does it work?  Can you do exports/imports without using the
incremental flag, such as for daily backups?

(2) how does Oracle load the data from the export file during an import? What
I mean is, if I export the desire tables in default (alphabetical) order, but
try to import them in a different order, it doesn't work. Do I have to
specify the import order during the export, and then let Oracle import the
file as-is?

1. The incremental functionality works like this (using export as an example).
Complete exports take everything.  Cumulative exports take everything since the
last cumulative or complete export (depending on timing).  Incremental takes
everything since the last incremental or cumulative (again depending on timing).
Clear as mud?

It's easier if you think of an example.  Let's say we do this on a monthly cycle
(assume a 28 day month):

Date      Export
1           Complete
2           Incremental (what's changed since last night)
3           Incremental (what's changed since last night)
4           Incremental (what's changed since last night)
5           Incremental (what's changed since last night)
6           Incremental (what's changed since last night)
7           Cumulative (everything since the 1st)
8           Incremental (what's changed since last night)
9           Incremental (what's changed since last night)
10           Incremental (what's changed since last night)
11           Incremental (what's changed since last night)
12           Incremental (what's changed since last night)
13           Incremental (what's changed since last night)
14           Cumulative (everything since the 7th)
15           Incremental (what's changed since last night)
16           Incremental (what's changed since last night)
17           Incremental (what's changed since last night)
18           Incremental (what's changed since last night)
19          Incremental (what's changed since last night)
20          Incremental (what's changed since last night)
21          Cumulative (everything since the 14th)
22          Incremental (what's changed since last night)
23          Incremental (what's changed since last night)
24          Incremental (what's changed since last night)
25          Incremental (what's changed since last night)
26          Incremental (what's changed since last night)
27          Incremental (what's changed since last night)
28          Complete (the whole shooting match)

Import can match this, so you could theoretically build a recovery from this.
The reason I say theoretical is that all we track in the data dictionary is which
tables have changed, not which rows.  As a result, if you change 1 row in a 5
million row table, an incremental export picks up the flag to say there has been
a change and exports all 5 million rows, not just the row that's changed.  That,
plus the fact that imports can't be combined with archives to perform
point-in-time recovery, generally means many clients haven't bothered with this
functionality.  The block level backup in Oracle8 makes a lot more sense if
you're at that level.
 

2. The default level isn't really alphabetic, but based on the relationships between
tables. It's important to not try and import table A with foreign keys pointing
to table B, before table B is imported for example.  Having said that, if you're
aware of these relationships you should be able to import tables in the order you
want, provided you follow this caveat - tables that foreign keys point to need to
be imported first.  The easiest way to manage this is to let Oracle import the
data.