To Turn Ten I have not yet to receive any gift cars for the advance in levels nor have I got the extra credits on level ups and another thing is every time I get a message it shuts the game down and puts me back to the Xbox one home. I am using the Forza 5 LE
The cars are gifted to you, you do not get them from leveling up in the game. The messages you are get are more then likely the messages for the gifted cars. As for the CR on leveling up how many are you getting? you should get 70,000 CR on level up if you have the LCE.
For the crashing I would uninstall the game and reinstall it and see if that helps. It has helped a couple of my friends with crash issues.
I have not been gifted any cars at all and yes I am getting the 70,000 credit and I have all ready uninstalled the game and also restored the system per xbox one support team Thank You
send Turn10 an email here forzafb@microsoft.com