1) Yes, one of its explicit forms is (ΔT) (ΔE) ≥ ℏ/2

2) Energy and mass are equivalent

3) Because they immediately recombine and annihalate, and there is no net effect.

Now you need to be careful how you interpret the time, T in 1). Its complicated, see an article by the cousin of a well-known singer:

http://math.ucr.edu/home/baez/uncertainty.html