Is T test similar to Z test?

When we use a z-test, we know the population mean and standard deviation. When we use a t-test, we do not know the population standard deviation and thus must estimate this using the sample data that...

a t test is used inplace of a z-test when the population standard deviation is unknown.

It depends on the population. Use t-test for a small population, N < 30; otherwiase, apply z-test or when N>=30.

When you don't have the population standard deviation, but do have the sample standard deviation. The Z score will be better to do as long as it is possible to do it.

Yes