It is safe. The erection will subside. May depend upon how attractive or sexy the laser operator.
Bruise. You may get the bruises or/and blisters.
Depends. It really depends on what tissue is being treated and why. I use pulsed dye laser (pdl) to treat warts on the foot (usually plantar warts). About the only risks are bruising, possible blister formation (this is rare on the bottom of the foot) and pain lasting for a couple days. It is very safe in trained hands.