Iphone purchased with emi can be used in other country?

If it is financed with a US carrier it will be locked to that US carrier. it can not be used on any other carrier until it is fully paid for and unlocked by the carrier it was purchased through.

If your friend buys it with carrier financing in the U.S., the phone will be carrier-locked to that carrier until the contract is fulfilled and the phone is fully paid off. Even then, the carrier might refuse to release the lock - since it is your friend in the U.S., not you, who they might consider to be their customer.

There is also the issue of whether your friend wants to be “on the hook” for the bill for the contract period. Maybe they’re fine with being “on the hook” but having you reimburse them; maybe not,

That depends largely on whether or not the phone is carrier locked.

I’m not really sure what you mean by “EMI”, but you can use your iPhone with other carriers in other countries as long as the carrier bands are supported by your country’s carrier. The USA model should work worldwide since they’re the only country with additional bands that other countries do not have but still have support for other bands. However, you should always check again with that specific carrier at: iPhone - Supported 5G and LTE networks - Apple

Also, keep in mind that starting from iPhone 14, units sold in the USA only support eSIM.

So if I buy that phone with that carrier can I use that phone in other country?

Yes, if the carrier offers an International Plan option. You would have to ask the carrier about this for more information.

And the warranty for the phone will only be good in the United States. You will not be able to get warranty service in Egypt.