Ok why is square root of 2 that is promptly squared 2 but when enter by hand then the result isn't exactly 2?

In decimal form the sqrt(2) is an endless string of numbers. So when you enter a fixed number for the sqrt(2) in a calculator you are entering an inexact value. When the calculator determines the sqrt(2) in evidently does the math to more digits than the maximum that can be displayed. So after the squaring process and the round-off process it is exact , but only to the number of digits shown.