for 1 a isn't grammatically correct while b is
for 2 both a and b are grammatically correct and have the same meaning
for 3 a and b have different meanings a is a more general statement while b is a a statement that is only applied for the time being a can also be written as every time she is late she calls us
4 a and b have different meaning a says I might help meaning that he is not 100% sure of he will help or not while b means that he will for sure help if he can't do it
5 both a and b have the same meaning while still being grammatically correct
