Fellow travelers - need your advise

We are going to Kolkata (CCU) next winter from ORD - we booked on LOT from ORD - DEL because the cost of business class directly to CCU was much higher. We will buy a separate ticket DEL-CCU. We do have a couple of options - Vistara and AI is on the same terminal, while IndiGo has lot more option by flies out of T1, which is a pain. Also, since I am sure Mrs. will pack heavy, I am now leaning towards Air India since both me and my daughter is *G (On United) - so we will get that extra weight.

So here is the question. My LOT flight lands at 5:00 AM, and the first AI flight is at 6:50 AM. Given all of us have OCI and on business class, I think, based on what I read here, 6:50 is risky. The next AI flight is at 12:30 PM - so a considerable wait, but seems like the only option.

So questions,

1) If somehow we land early or breeze through immigration and customs, in time to check and bag drop for earlier AI flight, will AI allow us to change the ticket free of charge since we are *G ? I saw something called priority airport standby on AI website but does not explain what it is.

2) I hear that you may not be able to enter airside until 3 hours of your flight at DEL. So that we do not stand outside for hours, should we not leave the arrival hall until the time is close ?

3) I assume we will have lounge access due to *G, right ?

Any other advise ?