If I completed an offer at a different site, and did the same offer with a new username at a new site, would I receive full credit for the offer?
Probably not, and it could get you put on hold.
yeah a pretty high chance of getting disputed
No, you cannot. This is considered fraud as the trials are offered to NEW customers only.
Odds are you wont be put on hold, but credit will probably be denied for both. Not a good idea, especially when there are so many offers to do.