Is there a chance that a baby can be viable before 24 weeks? if so at what gestational age (earliest) doctors will try & save a baby?

Doctors generally try to save all pregnancies that parents want to save and that don't have major fetal defects. Nowadays, if born at 24 weeks, about 2/3 survive; and about 1/3 of the survivors do well without problems. That means at 24 weeks, about 22% do well, 45% survive but have problems, and 33% don't survive. The odds get better every week, so the goal usually is to stay inside Mom longer.