I bought an xbox 360 and now want to download or buy a game. If I get an xbox one voucher like this on Amazon, it also applies to the 360. And if I have not given any real account details, will I still get the credit?
The money on the credit card will be credited to your Xbox live profile, regardless of which console it is on.
As long as the Xbox live profile is installed with the credit, you can use the credit as you like