and It must be signed by Black pen? I like blue ink pen.
Usually. There is a traditional exception in that a "holographic" will, one entirely handwritten by the person making the will, may be considered valid even when not witnessed. However, these days that requires a bunch of testimony by handwriting experts to be sure the person really wrote it, and even then someone might claim he was under duress, or not competent. Courts don't really like it very much.
I'm legal and have never had to be signed by a witness
It varies by state, but generally speaking at least two witnesses who are over 18, not related to the Testator, and not named in the document as a beneficiary or agent. In some states Wills also have to be notarized.
Yes,without two signatures the will is invalid, the witnesses cannot be in the will, see a lawyer to make it legal.
In most states, yes.
haha yes otherwise there is no proof of anything and anyone could fake a will
The law on that varies by state.
Not always, no.