Technically a car park would be ok, but the regulations state:

A horn should not be sounded when stationary on a road at any time, other than at times of danger due to another vehicle on or near the road.

A horn should not be used on a moving vehicle on a restricted road (basically a road that has street lights and a 30mph limit) between the times of 11:30 pm and 7:00 am.

Some (all?) US states have similar wordings in their laws as well but I've never heard of it being enforced.

Something not being enforced does not mean there might not be a good reason to follow it. Like for being able sleep at night without car honks

Totally agree, I never use my horn for that reason.

Pretty much everything impolite you can do in a car is illegal under some statute. None of it ever gets enforced regularly because the point isn't 100% enforcement, the point is to have pretext for fishing stops and for stopping people who did something the cop didn't like.

Your car also goes above 70 ¯\_(ツ)_/¯

Right... but it doesn't have a specific button that can't be used for anything else but going over 70?

6th/7th gear

Hey buddy, how can I get this car out of 2nd gear?

As I proved reciently on a trip through an area where the speed limit was 75.