Corvette C8 Z51 - Two Questions for a Friend

Hi All - I have a good friend who recently purchased a 2022 C8 Z51 - Beautiful car

He has one issue and one question and he asked if I would be willing to throw them out on FChat given that many folks on here either own or have deep knowledge of C8s and just the general knowledge depth and interaction in the FChat community even beyond Ferrari's. So here we go - any/all thoughts, input and feedback is always appreciated

Issue - Apparently a week or so ago he got a text from OnStar with regard to a fault code as well as his check engine light coming on - He took the car in and they performed some work and stated all was well - two days later the same condition occurred - Obviously this is warranty and am sure the dealership will take care of it but just wondering if anyone else has experienced this - Pic of the service ticket including the code below:

Question(s) - He has the factory 305/30/ZR20 Michelins on the rear but wants to swap for 315/30/ZR20s and get some additional contact patch but does not want to adjust offset or introduce any rubbing etc. So two questions:
1) Can he go to 315s without any issues?
2) Can he got to 315s on the rear without changing out the fronts?

Pic of the Service Ticket info below - Again, MANY THANKS for any feedback - Cheers

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