1. could this be applied to a vinyl convertible top?
sure it will stick
2.Can I use printer to add logo or text?
No, this is standard vinyl sheets.
3. Can it be used for other things, not just cars ?
Don't see why not. I was using it to wrap my macbook.
4. How many feet to wrap a full car?
depends what car you have. For most of cars, a roll of 1.52mx 18m would be enough.
5. will it work on car rims?
I wouldn’t think so, It might look like crap. this is basically a sticker.
6. will this cover a helmet?
Yes. But It might not stop rocks or scrapes from penetrating the film and damaging the paint surface.