hmmmm, did I test it you say... I did get the sector 5 key and saw Aeris' spirit at sector 5 church but it was so hard to catch her so....
and I haven't tested the "be bad to Tifa as much as possible" way bcoz I wouldn't be able to do that to Tifa, now wouldn't I?
but still, don't just do ths whole FF7 from the beggining just to see them results for yourself, it may or ay not work. Ask your friends or borrow a saved game with the events close to that of what you have to do to get Aeris back.