Can you register more then one of a single game to an account? ie: Multiple copies of a single game.

no

like if you have 2 mario kart? (im getting a second one for christmas)

probably but im not sure

gonna see then

Can I create a second account and link it with mine (a family account) and log the game on their for the points?

i dont know how to get family account to do that

When you sign in, on the left in the grey box, under the info where it says it says when you joined, it says set up family account.

Not sure if it works and don't want to really go through the trouble if it doesn't.

But, if it does I would just set-up a second account and exploit it when I need to register two or more games/consoles.