Would it be possible to add enough energy to a black hole to turn it back into a star?

Black hole to become star has to lose its enormous mass, but it can't do that. ... But supermassive black holes can transform into new state while we can watch a phenomenon like a supernova. Such black holes can give birth to new stars. But black hole itself cannot become a star again.

No, it is the compression of mass not the mass itself that makes the black hole.

If you could somehow add negative energy, maybe. Or negative mass. But if you could do that, you could reverse entropy, and be very powerful, indeed.

No.

You would have to "remove" mass (therefore energy).

No you couldn't

It would just grow and grow

If it didn't swallow the whole Universe, it would possibly turn into a White Hole

That is possibly how the Universe began, and Possibly how it could end

No.

All you'd do is add more energy/material to the black hole, increasing the size of its Event Horizon...

Adding energy to a black hole is like adding mass - it will just make the black hole bigger.

Black holes may power quasars, quasars can give off 25 TRILLION times the energy of our sun. That would be some laser!

...but it was the increase in energy that formed the black hole from a star. Adding more energy would just make the black hole stronger.