My hand scarred over after trigger finger release and is now disabled. I can't open my hand, grip anything, can't make a fist. Can this be fixed?

Most likely. I think that can most likely be fixed. Get it checked soon. The sooner the better.
Depends. ...On #1, your compliance with therapy- which should be by a certified ot hand therapist- before & after the next operation, operation by an experienced hand surgeon, your age, your physiology & how long the problem has existed.