If i take 2 classes each for summer 1 and summer 2 semester, will that be the same amount of credits like spring semester ?
Yes, as long as the classes carry the same amount of credit hours. You go to class more often and for longer time periods in summer classes.
Probably not. Expect to be short about 3-4 credits over a normal semester's courseload.
We can't answer that. Each class in the catalog will tell you how many credits it's worth before you enroll in the class. Look at the catalog to find out how many credits each summer class is worth.