Have L1, want to apply for H1, need some clarifications

[taruon]

Hi
I have currently on L1 which is valid till 2006 June. I am looknig for an H1 sponsorer. Questions I have are

1. If I apply now and my H1 gets approved, can I maintain both L1 and H1? If yes, for how long?

2. How long can I wait for my H1 stamping after October?

3. Do I have to immediately(on approval of H1 in oct) resign from my current company and join the firm who is sponsoring H1?

Will appreciate your answers.

Thanks

Taruon