COS from L1 to L2

[mangai1982]

I would like to know about the following.

1) How long does it take to change the status from L1 to L2?
2) Before the L2 COS gets approved, if I travel back to my home country, can I use my existing L1 to come to US again? Or should I still go for stamping?

Any replies, greatly appreciated.

Thanks,
Mangai