The built in hardware might not support all carriers, if it comes to LTE and 5G.
The supported iPhone 17 bought in Saudi Arabia has the model number 3519, the supported iPhone 17 for Bangladesh 3520.
Have a look at this article:
iPhone - Supported 5G and LTE networks - Apple
Also, the iOS is country specific, features which are not available in the country op purchase will still not work if you move to another country or region:
iOS and iPadOS - Feature Availability - Apple
And the warranty may be restricted by Apple to the country of purchase as well, in case of a warranty claim, you will have to send it back.
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Apple may restrict warranty service for hardware products to the country where Apple or its Authorized Distributors originally sold the device.
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copied from: Legal - Apple Watch Warranty - Apple