Unless you are an expert restorer, the short answers are NO, NEVER, NOT EVER, DON'T EVEN THINK ABOUT IT!
If you have a particularly dirty coin you might be able to remove some of the surface crud using a soft cloth and distilled water but you should never use any chemicals or abrasives. Home-brew cleaners (e.g. Tarn-X, lemon juice, dish detergent, etc.) may make a coin look better temporarily but will damage its surface in a way that will leave it open to more damage later.
Professional restorers have the knowledge and tools needed to remove things like scale and other crud from a coin's surface without harming it, but in many cases it's safer to simply do nothing to a dirty coin.
You can rinse and use a mild soap to remove excess surface soil. However, do NOT use any chemical cleaners (silver, nickel, gold or copper cleaners) and do NOT rub hard while using the mild soap.
No, as you can scratch the surface, thus decreasing the value of your coin. Coins are more rare if they haven`t been touched, scratched, or dented.
Broadly, one should not clean a coin. I do not suggest the cleaning of ANY coin. 99% of the time it does more harm than good to the coin.
NO, cleaning them will probably reduce their value
They are not rare.
Rare Coin Wholesalers was created in 1990.
You can buy them at coin dealers and coin shows.
Just the year does not make a coin rare.
No, they are not rare.
It's best that you don't clean it. Cleaning a coin reduces or kills the collectible value of any coin. The 1887 Indian Head cent is not rare it's actually very common, average circulated coins are $3.00-$8.00.
No.
It means that the coin is rare. For example a 1909-S VDB cent is a key date. This coin is rare.
Determine how many were minted, when and where and the numismatic grade and, last but not least, the availability of the coin for purchase
No and they will never be rare.