I quit playing after the first bunker season and recently reinstalled the game on my phone.
All the medals were gone, and there is no way to acquire level 5 bike parts (as far as I can see), since there's no longer a way to use rusty parts to make less rusty ones.

From the Platinum Knight costume requirements I can see I've already got 39 platinum medals, but none of them appear on the map, and the platinum requirements aren't visible.

Edit: When I wrote this, it didn't occur to me that gems and chips can be spent on bike part's.

Edit2: I'll also add that coin magnets and rarefied fuel are both unavailable to use, despite me getting them as slot machine rewards.