while singing air have to be pumped through lungs and diaphram and then passes sound through vocal chord in the throat,so if you practice in this way then your vocals will open up.
Singing won't do anything to your throat if you do it correctly. If it hurts or feels uncomfortable then you may be doing something wrong. Just make sure you have correct breathing and throat...
When you sing from your stomach or rather your diaphragm, the sound is usually stronger and your chest doesn't hurt as much. Usually you do that when singing a long phrase or loudly so you don't run...