Regarding unlocked iphone

Apple sells different versions of the iPhone 14 Pro Max

If you see an iPhone 14 Pro Max advertised for $1599, then it has 1 TB of memory. The iPhone 14 Pro Max that sells for $1099 has 128 GB of memory.

The phone will be unlocked.

For what it is worth, I would not recommend that you buy the phone in the U.S., but it is your decision.

Ask your sister to check and make sure that the iPhone is unlocked.

An iPhone 14 purchased in the U.S. is eSIM only. You would want to check with your carrier in India to make sure that they support eSIM.

If your phone requires service in the future, you will have to ship it back to your sister so she can take it in to the U.S. Apple Store.

The iPhone is unlocked.....unless.....the phone is offered as part of a special promotion with a carrier in the U.S.

Caution.......if you buy the iPhone in the U.S., it will have no warranty in any other country. In addition, you or someone else will need to pick up the phone at the Apple Store U.S. location, since Apple does not ship internationally.

In most cases, the best decision would be to buy the phone in the country in which it will be used most of the time.