Hemp twine (hemp rope) to support plants, can not cause pollination of plants?

water it, polen dies with water.

No

The manufacturing process would kill any pollen in or attached to the fibre. If your aiming to reuse the twine just soak it in water and let it dry in the sun and that will disable any potential pollen that was attached from it from your grow if any happened. little dish detergent never hurt either OR compost it and use new. Good Luck!

once unfortunately one of my harvest was completely ruined because of the male flower dust that I was probably able to take from my hand in the first weeks of flowering, I don’t want to relive it, and I don’t wish you either! always wash your hands when I get to the plants, I probably got pollen from my hand then because I was peeling an outdoor plant in front of it.

If your really worried try whipper snipper cord. I use this as its cheap easy and wont harm your plant.

No, these products undergo certain conditioning and natural treatments to get rid of microbial life and pests etc. You have a better chance at pollitnation caused by the mere wind passing through your house as male pollen can travel big distances. The hemp is a great idea for tying down branches etc. You have nothing to worry about :) Good luck!