The third and fifth option are most likely.
touching a toilet seat, holding hands, and using alcohol an drugs won't lead directly to contracting an STI.
The answer to this question is "immerse in cold water". What the responder or the person injured must do upon encountering or experiencing a first-degree or second-degree burns with closed blisters is to immerse the affected surface in a cold water. This will avoid further damage to the skin cells and tissues.
Pretty much, anything works. If you want to demonstrate bodily autonomy to a child, respect the decisions they make. If they make a VERY stupid decision, then tell them no.
If it's pretty much anyone, let them know you trust them.