1. This is undoubtedly a 1946-S sans-serif style mintmark
Lincoln Cent.
2. The condition of the coin is such that spending any time on trying to improve its appearance would be a waste of time. It's still a 3c
Wheat penny.
3. Whatever is on the coin and the problems it caused with the coin are damage to the coin, not the result of a mint error of any kind.
4. The mintmark is in a normal spot for any
Wheat cent.