Step 1 GC (I140) has nothing to do withvisa status, waiver, never been in US, illegal stay ......etc. This is qualification under certain category, either you qualify for or not. Step 2 (I485) which does need the waiver.
Can I ask for H1B extensions beyond 6 yrs based on cleared I -140 . . . . even if I haven't filed I - 485 due to ineligibility ?
Yes you can
What abt NIW category ? Am I eligible to file I 140 and I 485 at the same time before waiver completion in NIW category ?
No No No. J1 is a big barrier without clearing it with waiver or 2 year home country you can not adjust status under any category, NIW, family, lottry, whatever .....etc
thanks