Question about conditional

[Nikita 22]

Are these sentences correct?
If I had enough money I would have bought a car, but as I don't, I have to walk.
If I knew what was going to happen on a holiday I would have stayed at home.
or could I say, Had I known what was going to happen on a holiday I would have stayed at home.
If my sister behaved properly she would have got a present, but instead she was punished.

Thank you.

[J&K Tutoring]

Nikita22- when you have several examples, it's easier to respond if you number them.

1. If I had enough money I would have bought a car, but as I don't, I have to walk.
If I had enough money, I would buy a car but, as I don't, I have to walk.

2. If I knew what was going to happen on a holiday I would have stayed at home.
or could I say, Had I known what was going to happen on a holiday I would have stayed at home.

Your second example is almost there: Had I known what was going to happen on the holiday I would have stayed at home.

3. If my sister behaved properly she would have got a present, but instead she was punished.

If my sister had behaved properly, she would have got a present, but instead she was punished.

[emsr2d2]

Are these sentences correct?

If I had enough money I would have bought a car, but as I don't, I have to walk.
If I had had enough money, I would have bought a car but as I didn't, I have to walk.
If I had enough money, I would buy a car but as I don't, I have to walk.

If I knew what was going to happen on a holiday I would have stayed at home.
or could I say, Had I known what was going to happen on a holiday I would have stayed at home.
If I knew what was going to happen on holiday, I would stay at home.
If I had known what was going to happen on holiday, I would have stayed at home.

If my sister behaved properly she would have got a present, but instead she was punished.
If my sister behaved properly, she would get a present, but instead she gets punished.
If my sister had behaved properly, she would have got a present but instead she was punished.

Thank you.

I have some alternative suggestions as well as some the same as the previous poster. See above.

[5jj]

A couple of your sentences are grammatically possible, though I suspect you intended the versions others have suggested:

If I had enough money (i.e. if if were a person who always had money) I would have bought a car (some time ago), but as I don't, (I didn't buy a car, and so) I have to walk.

If my sister behaved properly (all the time) she would have got a present (e.g. on her birthday), but instead she was punished.