Country not supported in Apple Account

Indeed, Bangladesh is not supported. That's the problem with buying equipment for which there is no support in your country. You can use it for its basic features but the advanced one won't be available. You can ask Apple to introduce support but I have seen people ask about Bangladesh for the past 20 years so I would not expect things to change overnight.

Click on this link for Apple products feedback links --> Product Feedback - Apple

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Features vary by country. Not all features are available in all countries. If yours does not have a feature and you want to use it, you will have to move to a different country.