How do I clean my toilet tank by blocking the bowl water entries?

You can turn off the water at the wall to keep the tank from refilling to clean it.

You can just turn the knob behind the toilet off then flush the toilet. That will enpty the bowl and tank without messing up your toilet

I am not sure why you would want to clean the toilet tank unless it has rust build up that is falling in the water. In any case, I would try CLR which really does get rust, lime and other tricky stains out.

Sally is right about the CLR, it is an amazing product. Just be very careful not to get it on any of the plastic components!

And wear gloves when applying CLR.

Here's a post that might help - https://chascrazycreations.com/how-to-clean-your-toilet-from-top-to-bottom/