Question

For a freely falling object dropped from rest, what is the acceleration at the end of the fifth second of fall? The sixth second? At the end of any elapsed time t?

Answer 1

The acceleration at any time will be 9.8 m/s² as long as you are on earth.  The speed, however will be 9.8*time.

Answer 2

If you stay on or near the surface of Earth, then the acceleration due to gravity
is constant. It's 9.807 meters per second squared. (rounded)