Can i be a flight instructor at ATP if i did not go to school there?
ATP will on occasion hire outside instructors but it’s the exception rather than the rule. ATP offers it’s successful students a guaranteed instructor position. This is a very valuable perk as low time pilots often find it challenging to find time building positions hence these positions ALWAYS go to ATP students first.
Highly unlikely as ATP of course gives preferences to their own former students.
You can always apply, but I hear ATP has a surplus of CFIs and preference goes to successful graduates.