Various questions related to varicose veins

I have some questions about varicose veins issues in my calves.

Is it correct that varicose veins only appear in the calves and thighs?

It doesn't seem easy to perform vein surgery from a common sense perspective, so I'm curious about the principles of the surgery and the treatment method.

Are there no side effects after surgery?

When do you determine that surgery is necessary?

Please provide a response.