If I do the first boot in India with my activated Indian sim, will the iphone get activated?, or I need to first activate in US with any sim and then I can use it in India?
My understanding is that if you buy the phone directly from Apple or Verizon then it won't lock to the first carrier you try. But if you buy the phone from somewhere like BestBuy.com you get a universal phone that will lock to the first carrier you try, unless that carrier is Verizon. Regardless, it will activate on your Indian SIM. Whether it locks or not depends on where you buy the phone.
Verizon has agreed that in order to use some of it's LTE bands (I think it was band 13) it can't lock any of their LTE phones to Verizon. That's why the BestBuy phone won't lock to the first carrier if it's Verizon.
I watched Youtube video last night that T-mobile phones also didn't lock to T-mobile. I saw that the T-mobile phone was working on T-Mo and then he swapped SIM cards and it worked on Verizon LTE, it just didn't work on Verizon 2G and 3G CMDA service.
I don't have another carrier's SIM to try, and if I did try another SIM other than my ATT SIM, then my iMessage might try to add that phone number to my account, so I'm afraid to try it. If you are worried, you could wait another few weeks for Apple to release the SIM free version, but I think it's highly unlikely that everyone online is wrong about the Apple supplied iPhones and no lock.
This confirms some of what I am saying -
https://www.imore.com/how-buy-iphone-x-unlocked
[doublepost=1512245720][/doublepost]Also, this link helps (as of Nov 22 2017)
https://www.techwalls.com/buy-factory-unlocked-iphone-x-america/
To get an unlocked
universal iPhone X
online you must already have an active Verizon or Sprint phone line (not post-paid account), and if you buy it from Apple it will be unlocked to use with any carrier, including your Indian SIM.
If you have a friend with an account and they don't plan to buy one and agree to help you, then you can use their Verizon or Sprint phone number to order online. It will have to ship to the address on their Sprint or Verizon account.
The only other option is to have someone walk into the store and buy one, like I did. You don't need to have an active phone line to buy a Verizon universal model with CDMA and GSM in store, and it will work with any SIM around the world. And it won't lock to the first SIM you try.
Online reports are that ONLY phones bought from BestBuy that are SIM free were being locked to the first carrier you try, but they still worked with any carrier around the world, as long as you didn't try to activate it with another carrier first (Verizon being the exception).