The question about 'Power Back', meaning to 'reverse' the a/c has been asked several times in PPRuNe and a search will show them. The answers are expanded on the ones above. That is, high mounted engines are less likely to FOD and props with negative pitch will do the job. Most jets do not do this even if they technically can, due to risk of FOD.
The other key point already mentioned, when moving backwards - keep your feet off the brakes! Close the throttles/pitch to neutral and let her cost to a stop, then brakes, set pitch/throttles and move. If you touch the brakes, she will sit on her @rse and everyone will suggest that you had something to do with it.
In an emergency? In one of the earlier threads, there was a story from a ramp operative in the 1960/70s at LHR. Winter conditions with ice on the apron and a VC-10 arrives. As it closes on terminal and the air bridge - it started to slide forward on the ice. "Big noise from back of VC-10 and it stopped moving forward!"