Who was Zack? The only partner I remember from when Cloud was a Soldier is Sephiroth
Cloud was never in SOLDIER, (remmember in the movie they called him a "Would-Be" Ex-SOLDIER)
Heres an explanation from someone who has played the game properly:
Cloud basically in the FF7 Game is a friend of Zack and is going through an identity crisis because Cloud tried to sign up to join SOLDIER but he was turned down (cloud was however a Shinra soldier, just not the SOLDIER like Sephiroth was in). Cloud believes he was the one who did all the Shinra Missions along side his hero: Sephiroth (Sephiroth was legendary SOLDIER, everyone looked up to him), But that was actually Zack, Cloud just has his memory because when Cloud, Zack and Sephiroth went back to Nibelheim (all three of them were sent on the mission. Two SOLDIERS and a Shinra Soldier. You know this because Sephiroth complained a lot on the fact they had sent a rookie with them (that was Cloud)) Sephiroth Burned down the town then Zack and Cloud were taken away and experimented on. This is where Cloud started to experiance a problem with his memory. It became hard for him to remmember what had heppend in his past. But he got memories of Zack in SOLDIER and accidently got them confused with his own memories. So he thought everything Zack did was actually what he did.
Confusing aint it?
Cloud: Blonde Spikey Hair
Zack: Black Spikey Hair
Sephiroth: Long White Hair
what had happened to Jenova (I couldn't even remember what Sephiroth had to do with her, just that he was some sort of experiment).
remmember in the movie you see Jenova fly through space and earth captures it?
Before Sephiroth's birth, Hojo and Lucrecia were working as assistants to Professor Gast, Shin-Ra's top scientist, on the Jenova Project. The project studied the remains of an extra-terrestrial entity known as Jenova, which was mistakenly thought to be one of the Cetra (remmember, Aerith was the last remaining Cetra Descendent), an ancient people of the world that the game takes place in. Wishing to create a modern day Ancient, and believing that the blood of the Cetra was what would do this rather than the lifestyle of the Cetra, Hojo injected cell samples from Jenova into Sephiroth while he was in Lucrecia's womb.
I'm guessing that thing he does in the end against Sephiroth (the part when his sword breaks apart into several others) was some sort of Omni-Slash, can't say for sure though, since I never saw it in the game
It was Cloud's Limit Break specifically for the Movie