So the latest Captain Marvel Prime has a trait that states:
"when friendly character within range and lof is targeted with an attack, b4 the attack roll is made you may place may place Captain Mar-Vel in a square adjacentto that character and he becomes the target instead(even if he would otherwise be illegal target)"
Jason states:
: Mind Control. When Jason Wyngarde uses it as RANGE, he may count range and draw line of fire from any character he hit this turn and if he hits, after resolutions he can use Mind Control at no cost, but only to target a character he hasn't targeted with Mind Control this turn. (He may repeat this.)
Jean states:
Sidestep. Other friendly characters can target Jean Grey when using Mind Control.

So can I target Jean with Jason replace with Cap. Then after all resolutions finish repeat this action? Does the (illegal target) circumvent the clause in Jasons power bout önce per turn?

Mar-Vell doesn't change the fact that the original target was actually targeted (unlike Shape Change, for instance). Jason wouldn't be able to target Jean again.