L1 - H1: Minimum how many months L1 stauts should be maintained

[L1 to H1]

Please answer to the below questions.

1)Soon after i landed in US can i apply for L1 to H1 on change of status irrespective of quota,as i have already applied for H1 in the 6 years, if not possible minimum how many months i must wait.

2)If H1 approves on change of status, should i continue on L1 for one or two months or i must work with H1 employer from the date of H1 approval? Bcaz i can't leave L1 employer in the middle of assignment right?