#1
you know how when u stick the neck of you guitar really close to your cranked amp and hold down a string it gives this awesome feedback noise?? will that hurt my amp in any way at all? if so how? a cant imagine it being to great of the tubes or speaker
#2
It won't hurt anything.

BTW, you can get that same sound from a NOT cranked amp/guitar by using a Fernandes Sustainer.