Ok

i think that none of the experiments were clones. they were just peolple exposed to an extremly high concentration of jenova cells. these experiments were held in the shinra mansion (because the vats were zack and cloud were held are there and all the people in cloaks are in nibleheim).

Flash back about 25 years ago is were they excavated a "corpse" in bone town that seems to have extremly high regeneration as it comes to life almost as soon as taken out of its tomb. shinra (hojo) thinks that they can use this heigh regeneration and strenght to make a super soldier and so sephiroth is born and is a great success but shinra dont know that jenova is waiting untill sephiroth is powerful enough to free her to finish her mission that she failed to complete 2000 years ago. to feed on the essence of the planet.

unfortunatly sephiroth was thrown into the lifestream before the plan could be put into action.

now this is the dodgy part: one of my theorys is that she created another sephiroth to lead all the people with jenova cells to the northern creater so she could finish her job. the person who fits this bill is #1 who mysteriously dissapears after the all the stuff happens at the shinra HQ.

zack and cloud are also experiments but only cloud tested positive so zack wasn't affected but somehow cloud pulled through with slight amnesia.

i think that jenova is in control of sephiroth and everybody with jenova cells but only stick around with sephiroth because he is the strongest and has been exposed to the most amount of jenova cells

oh and after you kill 1 winged angel jenova dies. i say this because the in next battle sephiroth has no tenticles or stange transformations is very weak because he no longer has the power of jenova behind him.

whew :sweatdrop