Is cracking my knuckles really bad for my hand or my health? Because I am doing every moment, and also neck and wrists.

Crack away. There is no evidence that cracking you joints causes any problems.
Not necessarily . This is not usually a problem. Most likely you have hypermobile syndrome with increased flexibility, this gives more motion in the joint thus the popping occurs. The popping is due to the negative pressure from the increased jointpbement causing the fluid to sublimate to a gas that causes the popping sound.