Reminds me of when, as a kid, I spent hours making a model motorbike by cutting up chunks of polystyrene, then painted it with the Humbrol enamels that I had to hand.
It looked amazing when freshly painted.
Only to dissolve to a brightly-coloured resiny lump within a few hours. I was devastated!
So the humbrol enamel will dissolve the plastic bottle
No
the material doesn't allow hobby paint to adhered to it
Yes.
Bottles are usually polythene, which is pretty robust with regard to solvents, but for much the same chemical reason also pretty immune to having anything stick to it.
Yep.
No harm.
Other than the harm that would be caused by the solvent dissolving the plastic.
Which might have been mentioned once or twice.