Lol wut? He has to maintain status while he's physically present in the United States. Don't listen to people on Blind fosho.
Yes
You will still need to file another h1b (using your i140) so in case premium processing is suspended you would have to go through regular processing (just that you don't need to go through quota process again). Other option is to create back on L1. I am not sure if that is feasible in your company and these days rejection rate of L1 is high. I have done the same some time back (went to another country and came back on H1, with having approved i140)
But this h1b will be under cap or separate pool? Do we have to be picked in lottery?
If you haven't used your 6 years then it can be your old quota. Consult an immigration attorney for more complex scenarios
I think you can maintain your i140 and GC while in process as long as you get paid in the US.
Yup you can ... hopefully you’ll be able to upgrade to EB1 after coming back to US