Can only do it on a trampoline.

I can only do one if it's whilst falling from a cliff

I landed a backflip once off a snowbank.

I can only do frontflips. :/

i can do a flatground backflip...and front flips too :)

I can only do back flips on a trampoline.

I can if I'm going off an edge onto lower ground, off a diving board or on a tramp. The closest I can do is a back handspring on flat ground, which is difficult even then as the last time I did it I hit my head on some grass.