As far as I know the car can come in and be worked on for as long as needed while the race is on.

Much like Le Man's. However most teams don't bother to repair because F1 is so fast, and the race relatively short, you'd never make back the places and likely finish last anyway. Might as well spare the car.

I don't see that they did anything wrong by serving the penalty however unless there was a major issue with his car, he should say least have carried on racing to the end. But it doesn't make a huge difference anyway. I think they did it just to avoid further penalties.

IMO the car was fine but Checo had enough. He just was in the poor frame of mind making mistakes everywhere and couldn't snap out of it so he thought he might as well give up.

Not very sporting or professional but what can you do?

Typically in F1 ever since I can remember, and I've been watching since I was about 3 years old in 1978, the unspoken rule is that you keep on racing to the very end, no matter how hard it is, unless the car is permanently damaged. Giving up want an option, especially in F1 where anything can happen and all of a sudden your might find yourself in the points after all.

This has happened many times due to accidents, blowing engines, rain etc