as it seems you need then 3 friends. tried it out with someone too but couldnt get it going while with single search you had plenty of people to play with...
No, but you can try to start a search at the same time as your friend and there'll be a pretty high chance you'll land in a match with them and another person. I've done it before easily enough.
Depends which one, one of the you can invite a friend but the others you can't. The tag team one you can do solo now by picking two characters then swapping them.