Does a black hole become a normal star again?
There's several ways this question could be answered, but they all come down to an emphatic "no" - a black hole will not return to being a main sequence star. The simplest way to see this is probably that a black hole has a much higher entropy than a star or even another type of stellar remnant of even vaguely similar mass and so there simply could not exist a spontaneous process by which a black hole develops back into a star.
A black hole once formed will stay a black hole, however it is believed that the Hawking process will lead to the black hole eventually evaporating. The time scale for evaporation though of a stellar remnant black hole is mindbogglingly long and they will not evaporate until long after stellar formation has ceased in the Universe.
A very long time indeed. Hawking radiation won't even be a consideration until the influx of mass/energy into the black hole drops below the rate at which Hawking radiation dissipated mass/energy. For a stellar black hole, even the incoming photons from the Microwave Background Radiation swamp Hawking radiation. The universe will have to get a lot older and a lot colder before black holes (except for tiny ones) stop gaining mass.
For anyone who doesn't want to do the math, he's a very convenient Hawking Radiation and Black Hole calculator: http://xaonon.dyndns.org/hawking/ - I can't swear to it's accuracy though. (and this doesn't take into account background radiation input, so, that changes the time a bit)