I would appreciate the info as to how I can do the challenge with out the 15th Anniversary edition.
Thanx for the reply.
I thought that I did provide an explanation, but perhaps you didn't click on the links I provided such as
this one to GTPlanet’s Guide to Gran Turismo 6 Pre-Order Bonuses?
The point is that 15th Anniversary
cars are not exclusive to the 15th Anniversary
Edition, and that the original poster's assertion to the contrary is incorrect. Most people who pre-ordered the
regular version of the game received a pack of
some of the 15th Anniversary cars. There is five different car packs: Precision Pack, Torque Pack, Performance Pack, Adrenaline Pack, and Velocity Pack. Each pack contains five cars. The available pack depends on what retailer and in what region the game was purchased from. The 15th Anniversary Edition of the game includes all five packs, in addition to other bonuses of 1m credits, paint chips, race suits, helmets, and avatars.
As I pre-ordered the game in June of last year from a Canadian retailer, I received the Precision Pack: Tesla Model S, Chevrolet Corvette Stingray C7, Audi R8 LMS Ultra, SRT Viper GTS, and Nissan GT-R Nismo GT3. This is the most common pack, as it was included with pre-orders from any retailer worldwide (excluding Australia). The 15th Anniversary Edition wasn't available or even announced at that time.
Of course, pre-order bonuses aren't any help to you now unless you acquire a code from somewhere such as ebay. However, it's possible that this is the final event featuring 15th Anniversary cars. I can't confirm if that's true, but others have speculated as much, and it seems plausible.