if i reheat a piece of wood that has been previously straightened by dry heat will it return to it's original shape? ( no other forces applied)

It might creep a little but dry heat bending tends to produce a stable bend for the most part. It depends on the wood and a number of other factors. Just keep it bent in a vise with weights or forms, apply heat and bend as desired.

What are you trying to do?

tried straightening a sidebended stave but added some deflex while doing it...

I have taken the twist out of a stave by hanging a weight off to the side, then heating the wood until it went just a little past where I wanted it to go and then letting it cool.  And then repeating until the twist was gone.  I started at the middle, not the end.  And the wood was red mulberry that I had chased down to one ring.