is 100 in toefl exam a good score?
Yes, for virtually every college.
Agreed. And once you hit the threshold for the college, whatever it happens to be, scoring higher makes no difference.
I scored 22 in the speaking section. I read about some colleges that require 25 in the speaking. Is that really bad ?
That’s a different situation. It would depend on how flexible the college is. Many will not be.
Once again, I agree with @TomSrOfBoston . In general, a requirement is a requirement. Flexibility on deviation will depend upon the school, so your best bet is to ask the school directly.