In USA from 2013 in L1A & the same employer filled for H1b,can I transfer the H1B to other employer& when.

I’m at USA & an India citizen.I’m with the employer under L1A .Working in L1A for last 3 years & has recently being renewed till 2017. H1b is filled by the same employer & approved & will be active from 2015 Oct till 2018.
So now I have two petitions (L1A & H1B )
Can I switch employer using the H1B ? When can I do this?

Yes you can switch employer using H1 approved petition. You can do it anytime but it will only come into effect since 1st Oct 2015.