im trying to buy black ops 1. You can't buy 360 games on the Xbox one, only online or on a 360. I bought a gift card, but the Xbox website only takes credit cards for 360 purchases. I tried to buy it on my 360, but I have a 4gb console and it won't let me even buy it. So my question is, if I get my friend who doesn't have an Xbox one, only a 360, can he sign into my account on his 360 and buy it. Will it transfer over to my Xbox one? I haven't transferred any games from my 360 to my Xbox one. Thanks.
I'll try to answer or address all your points.
First off, you can buy 360 games on the One. The reason you aren't able to is most likely because of your payment method. I personally think the easiest way is to buy a currency card and redeem it.
Once you own a content, no matter where you bought it, you can download it to any console your profile is logged in on. Should the title have been backwards compatible, it will also show in your Ready to Install list on the Xbox One games app.