OCD changes once in a while, not really but when new seasonal events are added
UCD is tied to grinding, if you want an specific car, you'll have to race and race until you get it, or "do" 5 licence tests, then check your UCD and keep going until you get it 👎
Best way is with a lvl23 ticket 👍 a 2001 ticket can do it, but it's a lottery with hundreds of cars...