I am a welder for 5 years now with certs and a degree. To answer your questions
1. Can be immediately dangerous sometimes like a big chuck of steel falling on your head. Most of the danger is from smoke inhalation, arc flash and loud noises thar will slowly get ypu
2. Cool shit is what you can create. Welding is nothing more than a nail to a carpenter. Exotic metals are cool to weld but will kill you faster
3. Yeah if you know what you're doing you fucking retard
4. Welding is the bond between two distinct pieces of metal. What do you think.