You should just be able shine an artificial light source onto it to turn it back white again don't know about just UV though , you should try it and let us know!
Op - you mention lettings agency, does this mean you are renting?
If so the eicr and associated costs and remedial work are the responsibility of your landlord and not you.
Don't forget it's very hard for us to tell you what colour it is due to differences in colours on monitors and phone screens and the like.
It could be cream , it also could be ivory
Drill out the rivets and replace with the same size (you will need a rivet gun)
This will be easier with two people one up a ladder holding the window and the other drilling/riveting
Normally it's because the wire that connects the button to the toilet is twisted or caught or has too much of a bend on it to operate correctly
Have you played with it when its loose like in one of your pics?
Failing that new flushers only cost a tenner
Then simply change the pendant, very easy and cheap to do , two wires is all you need to change.
You could change the holder only as well , lots of options , no need to buy a converter
You probably have worn down your clutch a little bit hence the smell
Why did you feel the need to rev a lot? Reversing up a hill is no different to driving up a hill forward , do you rev a lot when driving up a hill forward?
https://www.google.com/url?sa=t&source=web&rct=j&url=https://documents.4rgos.it/v1/static/8374037_R_D001&ved=2ahUKEwjP3pLiw5LvAhUhpHEKHSPbDSYQFjAAegQIAhAC&usg=AOvVaw3X5nIKOQwoQr5oHEvb0QdT
Page 24 may be helpful for you