1 X Rust Eraser Sabitoru M

I have an amazing carbon steel knife that is badly tarnished & a shows minor rust. Will this product help with tarnishing? Or just rust?

I just got 2 used ceramic whetstones at a thrift store that have little wear but both have rust on one side of them. will rust remover work on stones?

Can i use this on my diamond stones

when should this item be replaced? how long will it probably last?