It is true you are required to have a hi viz jacket with you in case of an emergency, you don't have to wear it whilst riding.
The rules with regard to the reflective sticker only applies to helmets being sold in France, if you bring one from outside of the country it's no problem.
Some other rules to keep in mind:
- Riders and passengers are required to wear gloves (with a CE certification)
- You need to have a breathalyzer with you
- Your navigation isn’t allowed to have an option that gives a speed camera warning