Empty bowl of water wit a disposable cup. Spray hard ring areas wit white vinegar let sit long as u can then scrub wit a Mr majic white sponge moistened wit more vinegar and bake soda.
Vinegar and baking soda
This works on everything in the bathroom
Heat up 1 cup of white vinegar, mix in about 1/4 cup of Dawn Premium. Not the dollar store kind, because it is too thin. When mixed, pour into a spray bottle and fill with water. Shake. Spray down the grout and let it sit overnight. In the morning rinse. If you have stubborn stains, spray again. Use this mixture a few times a week. It will keep your grout and tiles clean. Also works wonders in the toilet bowl to keep hard water stains at bay. Oh you only have to heat the vinegar one time when you add the Dawn. If you can let it sit in the potty overnight, then clean with a scrubbie. Once clean, spray a few times a week. The hard water stains do not come back if you spray weekly.
Vinegar! It dissolves lime from hard water.
Try Coca Cola- https://www.craftylittlegnome.com/clean-toilet-coke/