Are workplaces allowed to deny a place to sit, breaks, as well as bathroom breaks?

That is a really really dum way to run a business, but a few people think they can command people to hold it in. I once worked for such a place and when I had to go I locked the door and went. The company eventually had to find a new manager. The new one was no different, so I quit and found another job. You don't have to put up with such conditions, and you don't need a law to protect you.