can employer invalidate H1B Visa when i change job

Hi,

I worked for employer A, They sponsored my H1B and travelled to US and stayed there for almost a Year. After I returned to India my visa expired and changed my job to Employer B. (almost 3 years gone)

Is there a chance to apply for extension of H1B or my employer A would have invalidated it.

Thanks!

Extension needs to be applied by an employer.

So if you have left A, then B can file a cap-exempt petition for you (transfer + extension). This can be done even if A has revoked the petition.