Can't download on 360

I change the region based on my current situation, usually setting it to United States most of the time.

That's usually the sign of a region issue. Does your account region match your physical location?

Edit: Since you mentioned it in another thread, it's definitely a region issue. many 360 games were region locked so in order to download them your account region has to match your physical location and you have to be in a region where the games were released. Since you are in an unsupported region, you won't be able to download those games.

But you are physically in Iran, it doesn't matter what you do, you must use the region you are in,

Iran has never been an Xbox territory and is currently under international sanctions legally preventing Microsoft from supporting you like Russia, even if it was ever an Xbox zone

This means it doesn't download completely and doesn't run. Most of the time, this problem occurs around 80% of the download. And it gives the error can't download.

i'm sorry backwards compatible games are no different from regular Xbox one games

what specifically is your problem?