I thought the instant coffee would make a good pre-workout shake by blending it in with protein.

Technically, no. The caffeine will release when it reached the acid in your stomach. But more caffeine will be released if you use hotter water than is in your stomach.

Because i don’t have a coffee brewer i heard about applying it to your hair to stop shedding but that instant coffee isn’t good to use because of the additives in it because it could be damaging to the hair so i was wondering if i boil the coffee will the additives lessen or go away completely or not at all?

Not unless they have a boiling point under 212 degrees Fahrenheit (which is the boiling point of water), in which case they will vaporize before the water.
The only other way to separate chemical components is by spinning in a centrifuge.
I think your best bet would be to buy the regular ground coffee beans.