Why iphone are black listed?

I have two question.

1) My friend living in USA and he is coming to India. I said him to take a iPhone (On contract that cost 200$) with him. The iPhone he brought from USA to india have any issue in future regarding contract he signed.
Because he have to go back USA after some day.

2) What are black listed Iphones and why they black listed?

Your friend can brought it to India but can't use it with Indian telecom service providers. He can use it if roaming supported for contracted telecom company. Another way you can jailbreak and unlock iphone via software or Gevey sim depending model and modem firmware of the same. After leaving to USA you can restore it and can use as usual in USA. I have not a clear idea what is black listed iphone, I think if you void or failed to pay bill or stolen phone etc, these are blacklisted on apples server via their IMEI number.

1. The contracted iPhones can't work in foreign countries. They are locked to the network they came from.

2. Could be lost or stolen.

  • Which kind of Rock Space power bank listed below would you prefer to buy with 1000 INR differences between each kind? 20000 mah (can charge 5 times for an iPhone) 13000 mah (can charge 3 times for an iPhone) 10000 mah (can charge 2 times for an iPhone)
  • What are reasonable prices for the listed iPhones? What price is reasonable to pay for these iPhones in decent, working but used condition: -iPhone 1st generation: -iPhone 2nd generation: -iPhone 3g: -iPhone 3gs: I plan on buying one those phone (don't want to buy any new model, and for a specific reason), but I don't want to overpay. What prices should I be willing to pay (at max) for each?
  • Secondhand Iphone 4s won't work, is it black listed? We brought it from Amazon from a seller with a good reputation. But i feel now we have been ripped off, they said it wa unlocked to Virgin, Orange and vodaphone, but it doesn't work on Virgin or Vodaphone. We took it too one of the shops that unlock phones and he said it was blocked becase of an insurance claim. The seller said he doesn't understand, so now thinking we have be scammed. as anyone got any ideas to help.
  • My iphone went black but not totally black and i don't know what to do? So i was on my phone and i opened up the snapchat app and it just froze and went black but not totally black like how it is when it is off you can still see a little light. I really have to have it for tomorrow and i don't know what to do, i tried pressing the home and top button at the same time but its not doing anything.