Any helmet would help yes.
Yes bit I don't recommend it. A skate helmet is designed to protect you in ways a bike helmet can't. Skate helmet is designed to take the banging and full head protection where a bike helmet isn't
well, if you need helmets in the first place, stick to bikes- it's safer. but if you really want to skate, then i guess it's ok. better safe than sorry. common skateboarding injuries are abrasions, more serious ones are concussions and fractures
If you ask questions like this, i suggest wearing one 24/7 imo.
I was wondering cause I dont have any skateboarding helmets.