Non Cap petition from India

[ghole]

I got my H1B stamped from company X on Aug 2011. (VISA stamping is valid till MARCH 2014).

Now Company Y wants to file new non cap petition, so that I can join them in USA.

I never traveled to USA on H1B visa I got,so I don't have any pay-stubs for company Y.

Questions are -

1. Once approval notice comes for employer Y, can I travel with old stamping and new approval notice ?

2.If we compare filling new H1B from company Y, against non cap petition (visa transfer) from COmpany X to Y, which has more chances of getting approval ?

3. If my non cap petition with company Y gets rejected, then can I still travel with company X approval notice and visa stamping ?