IPhone – get the own text message sent back to me in a group message on iphone 5S

This is a known issue with iMessage. In your case, what has happened is that the SIM was registered on Apple's servers as capable of accepting iMessages. When your friend swapped phones, they likely kept the same SIM card. So now their old iPhone (bound to Apple's servers by its UUID) and the SIM card (bound by its own ID) are both registered with Apple to receive iMessages.

This article talks of possible fixes, and the possibility that Apple has something cooking (after all they should provide some capacity to remove the devices, perhaps from your Apple ID account). You can also head over to this article for additional reading and perhaps more solutions.

I wish I had a simple solution for you, but it may require calling Apple and discussing the matter with them. I would say you should also ask them to cover the cost of a new SIM should your friend require one.

In my experience I always see all recipients in a group iMessage - so depending on if the author of the message chose email or phone numbers I see each recipient's information.

If I have that address/phone in my address book, then I get my address book's name for the contact, but even then, I can tap on the name and determine if an email or phone number was used to address the group.

On the iPhone, there is a group message toggle - but at iOS 5.1.1, it doesn't seem to matter whether this is on or off on the sender or the receiver - I still see everyone in the group iMessage. As far as I can tell, that switch doesn't do anything on an iPhone and isn't there to even help on an iPad / iPod touch.