Yes, at best your whole mouth will go numb, and unless you got a dentist appointment its a waste. That's what people do after snorting a line, if theres residue, which there normally is they'll put it on the gums. I've done it enough.

And yes, smoking it powdered wont really do anything.

And again, it can cause problems even without a heart condition, but only taking it once wont do much. It's a stimulant and in effect speeds it all up. It's like speed. If you take lots and lots of speed all the time your heart get bigger and bigger as its a muscle... its grows because its going faster.

This can cause big problems,... BIG.

Like i said, i doubt it really is coke, but try a very small amount and see if its legit, if it is its up to if you want to smoke it but remember its just as easy to sell it on and get the good ol' plain 'erb.