Is it possible to downgrade from 3M5 to 2.0.0.2 iFix2?

Hello,
I would say this is an unsupported scenario.
What I usually do to test the migration:
1 - do a 2.X export of my repos db - repotools -export
2 - do the 3.X migration
if something is wrong or if I want to go back to 2.X
4 - do a 3.X repotools -dropTables
5 - do a 2.X repotools -import

note that following the above steps is a kind of "revert to snapshot"
where you'll loose all the work performed in 3.X.

Thanks.