Apple ID

Changing it how ? If you mean you changed the primary email address on the account (What to do after you change your Apple ID or password - Apple Support) to see what you can redownload : Redownload apps, music, movies, TV shows, and books from the App Store, iTunes Store, and Apple Books - Apple Support

If you created a new account and want your purchases linked to it, you will have to buy them on it

If you aren't receiving the code contact iTunes Support : http://www.apple.com/support/itunes/ww (click on your country's flag, the country where you live, and which is therefore the country on the account ; click on Contact Support towards the top right ; click on Get Help under 'Talk To Us’)

You have to live in a country to use its store. If/when Apple open an iTunes Store in Burundi, or you move to a country that already has an iTunes Store, and you are able to put your real address on the account you can try contacting Support.

That's because there isn't an iTunes Store there. What country is on the account, and when you will be back living in that country ?

Get them cancelled : https://www.apple.com/emea/support/itunes/contact.html