Does low gravity exposure to early stages of human fetus have potential to unloc unused genetic information from earlier stages of evolution?
No
The question itself does not even make sense, we do not hold onto much unused information, there is nothing to unlock. Unused genes mutate and get co opted for other purposes. We have about a hundred new mutation per generation. Much of so called junk DNA is actually just used for other purposes besides coding for proteins. 

Will a colony evolve differently sure, any isolated population evolves along its own lines but it will happen at evolutionary speeds.