is y=(1/2)(g)(t^2) the same as radical 2y/g=t?

Answer 1

You're very close, but there's a small mistake. When you take the square root of a squared variable you need to use the absolute value of that variable, or you need to restrict the range of value for y to denote that it is positive. (I'm assuming you're working with the real numbers and not the complex numbers. If you're working with the complex numbers you are right.)

Answer 2

Yes.

Answer 3

Yes, that is correct.