Earlier today, I saw an interesting app is currently on sale so I decided give a surprise gift to one of my friend because I thought he'd definitely like it. But I'm not sure if he has that app already or not. If he already has it, will App Store check whether that email account already bought that app and warn me? Will it be a refund later? or the money would just go waste? And are there any way to check if my friend is already have this without asking him directly? Please tell me, thank you.