If I am invited to a game but I don't match all the prerequisites. Should I join anyway because I was invited & see if I'm refused or decline because I don't qualify.?

I think that you can join some game where you're invited, even if you don't meet prereqs

You can ask the one who invited you in the game chat, right?

@Widzisz... not in 2.1... you need to create a forum post now that Fizzer rolled back options to communicate.

See:
http://blog.warlight.net/index.php/2013/09/website-update-2-1/