If the lower jaw moves forward due to tmd, does it retake it's former position afterwards or will it stay like that forever?

Depends: If the tmd has displaced your jaw to an uncomfortable position, you may need splint or manipulation therapy or even surgery to correct the problem as your disc may be dislocated. Sometimes treatment may result in a new jaw position that is more comfortable but may require alterations to your occlusion to manage in the long term. Please get evaluated by a knowledgeable practitioner to know.

Depends: Depends on what's causing the joint discrepancy. If you have a problem with teeth/jaws not fitting properly, especially if the jaw joints are being adversely affected, see an orthodontic specialist.

Maybe but...: You may need some therapy/exercises to reposition the jaw joints and a also a mouthpiece to act as a MORA (a mandibular repositioning orthotic appliance) to reprogram your bite. A TMJ specialist is probably your best bet.

Depends: Depends on circumstances. See a TMJ expert to examine you and give expert advice.