I worked for company a in India for 2 years and came to US for the same company on H1B - My HR is advising me to transfer to L1A for Processing Green Card under EB1C ( Executives and Managers) category for faster processing.
My question are:-

How much time does it take for a H1B to L1A transfer?

Can I transfer from H1B to L1A now and again back to H1B( if for some reason I want to change my job in US) OR will my H1B cease to exist.

You may apply for change of your status from one category to another but H and L are included in the same quota. So you have 6 years term max for each or both.