I am on the latest update, so yes, I am at 2.12 or more.
And I can confirm after doing the 24hr Nurburgring race that after I received the XP (about 4 million), my B-Spec level decreased to 32, it was at 25 before I used the save editor, so yeah, it reverted back and the new XP I gained was put on top of the level I was at before (25).
But for me personally, this isn't a problem. Since I can now do the Red Bull challenge anyway without spending so many hours grinding on the same boring races to get to level 30.
I've done it all in the past, back when the game was released, I bought day 1 and after about a year I had platinum, but I lost the account and I also want to record with my new capture card, my feat of achieving gold in what's considered by most, the hardest Gran Turismo challenges in the history of the game (the Red Bull X challenges GT5 ver.).
Grinding to level 40, A-spec was one of the most painfully boring grinding experiences ever. Level 40 B-Spec you could just replay several endurance races without even lifting a finger, but on A-Spec it was just plain boring. By the time I have nearly 100% game completion and I'm not level 40 A-Spec, which means I can't do the 24 hr Nurburgring A-spec race, I'll just use the save editor for that and do the race and end it like that.
Also, another few bugs I had were that a few cars in my garage were not displaying the icon (the car icon profile pic) but I could select them, see them on display when choosing them and use them in practice or races. But still, I decided to remove them and buy them again (they were fortunately only cheap cars) and now their icon appears and all is normal.