u/CyphrKey

We picked up an old (20-30 year old) puzzle from a yard sale, and noticed that some puzzle pieces had small darl discolored smudges throughout it. Is there any way to remove them without damaging the puzzle pieces?

As seen in attached pics, I'm going to regrout several small areas in powder room where grout became loosened/separated. The damaged areas are small and do not extend across a large surface area of the floor. Can I just regrout over the damaged areas or should I scribe the length of the tile of each affected area with a utility knife to remove the old grout before regrouting?