There is one part in FF7 which has been confusing me for ages when cloud has his real flashback to what happened in the reactor (when Sephiroth is leaving) it looks like sephiroth stabs cloud but gets thrown over the edge what is happening here?

And another question is why is sephiroth stuck in the promised land and how did he get there.

In response to the first question Sephiroth IS stabbing Cloud.

And as for the second question Sephiroth isn't stuck there against his will, he made a barrier so that no one can get in or out, and he got to the promised land in the same way you did (By travelling) you should have been able to work that out just by playing through the first disc (How you were on his trail).

I think you've answered your own question...

... The promised land, in my opinion, refers to a place where the Cetra return to at the end of their lives. A place filled with Mako. The planet naturally consists of lifestream within the planet (lifestream basically being the same as Mako.)

Now, in Cloud's real flashback, you see him attack Sephiroth with Zack's sword and wound him. He then goes to attend to Tifa, and Sephiroth walks past. Cloud goes and tries to finish the job, but Sephiroth stabs him through the shoulder / chest. Cloud grabs the blade and throws Sephiroth down into the Mako reactor, straight into the heart of lifestream (notice the blue / green glow under the reactor?) The injury to Cloud means that he requires Mako treatment and such like to be rebuilt.

As a result, Sephiroth is absorbed into the lifestream (stuck in the promised land, so to speak.) Sephiroth is encased within that crystalline structure, and gathers in a place where the lifestream can escape from the planet (the Northern Crater.)

To be honest, most of this is pure speculation. This is how I'VE pieced together the parts of the story, some other people may have different ideas, and these might be better than mine. This one makes the most sense to me though, so I hope it helps you out.

And as for the second question Sephiroth isn't stuck there against his will, he made a barrier so that no one can get in or out, and he got to the promised land in the same way you did (By travelling) you should have been able to work that out just by playing through the first disc (How you were on his trail).

I thought that the sephiroth i was following was a clone or image to lead cloud straight to his real body