Issues When In Opt & H1 Processing And Get New I20's

[phoenix_nebula]

Can any one tell me how sevis works?

1)My H1 is still processing..but my OPT ends in July.So if i request new i20 from new college will that be a problem???
2)I know they will generate new i20 based on my old i20's.But when sevis becomes active?
3)when it gets active in school will that get invalidated in other school?
4)At what point of time it becomes active?when i pay fee? or when I20 geenrated for first time??

please explain in clear, as these things are eating my mind and having sleepless nights.

ThnX