Just looked again at the "Warthog" and the "Actaeon".
For both the "Active" suspension is available for purchase without the upgrade. Without you can buy it for 9800 money (at the left), after finding the upgrade it's on "X1" (at the right).

... just like PTS 7.0.

Same for the "Actaeon"

I don't understand. In a new game, you ned to be rank 26 to unlock... Usually, "Explore Kola Peninsula ..." will appear there.

Then what is the upgrade useful for?

Old thread... https://forums.focus-home.com/topic/52731/upgrades-for-the-warthog-are-all-unlocked-from-the-beginning