No the message that pops up at level 30 just SAIS that you can by it from now on (at least in the german version of the game) - but you can only look at it in the dealership - you can BY it when you are level 40.
You can get it for free if you really want - there's an American dude on here duplicating them and giving them away, all you got to do is ask him and send him a friend request. 👍
You can also grind Bob to lvl 35 B spec, and then it's a free trophy car. That's how I plan on getting one, since my B-spec level is way higher than my A-spec.
I don't think you gain any more real driving experience going from level 30 to 40 since the only races after 25 are enduros.
Also since the X1 is not real and doesn't really drive like any other car in the game, even being really great in the FGT car doesn't get you out of the mindset that the X1 does things you don't think you should be able to do in a car. You have to make yourself take corners faster then what your brain wants you to.
If you take the challenge you get around 500,000 exp points for each race that you bronze. I was at lvl 24 on a spec, I unlocked the challenge from b spec lvl 30, and I went to lvl 26 with one bronze. Then I went to lvl 28 with a bronze in the second race..... It was very nice! I haven't beat the third race yet though so no X1 for me yet.
I have 3 of them. 1 for reaching level 35 on b-spec & 2 for getting silver on the Vettel challengers. When I complete the challengers with all gold & I get my 4th 1