I received some bitcoins from a friend and he sent them using the official bitcoin app, I received those coins with the official app.
I sent him an address via hangouts to send the coins too and he did, they turned up in my account instantly.
Wonderful. I'm glad to hear that bitcoin is working well for you.
Not if he sent you bitcoins and they turned up you didn't. That address has never had any bitcoins sent to it, and has never received any bitcoins. You are either lying or mistaken.
That is a very bad idea. Just because bitcoins were previously received at a particular address is no guarantee that the address is still associated with the same person. You should ALWAYS get the bitcoins address from the person that you are sending the bitcoins to and never try to guess what address you should use.
Again with the mistakes (or lies). That is not even a valid address. It is not possible to send bitcoins to that address. Any half-way decent wallet will inform you that it is an invalid address and will refuse to send any bitcoins.
Can't tell you why until you provide accurate information about where you received them and where you sent them. Perhaps your wallet never sent them (since you used an invalid address), or perhaps they arrived at some service (if your friend sent from some third party service), or perhaos something else entirely has happened. We can give you a better understanding once you explain better what happened.
That's not how bitcoin works. You shouldn't assume such things.
It might be a good idea to find out. It also might be a good idea to figure out what addresses the two of you actually used (since you certainly didn't use the addresses that you've posted in this thread).
Probably, but maybe not (under some very special circumstances). Why take the risk? If someone wants bitcoins from you, you should always require them to provide a valid bitcoin address.
You're Welcome.
These aren't mobie phone numbers. These are bitcoin receiving addresses. Why would you just assume that they work like mobile phones? Don't do that in the future, you're likely to end up losing money.
It might be. It might not be. Why take the chance with trying to guess whether it is or not in a particular situation? Just get a bitcoin receiving address from the person that wants to receive bitcoins and you won't have this problem.
That's because you thought that a revolutionary and brand new technology works just like a mobile phone number. Stop assuming such things and you'll be a lot less confused.