Hi ya
My brother-inlaw had the same problem with his toilet. I thought I was going to throw up when I saw it. It was like it was baked onto the toilet bowl and know matter how hard you scubbed it wouldn’t come off. So I poured about a half a cup of Caustic Soda or the common trade name is Dranio, into the toilet and left it for about an hour then flushed the toilet and gave it another srubb and was all gone.
To remove grout you can use a single edge razer blade or what I used was a tool called a Grout remover. I found it easy to use because it had a handle on it and it made it easy to hold. Regards Noelene