Questions about Crayola Ultra Clean felt tip pens with cone tip

If you want to decorate the windows with it, probably not the best choice. The come off easily but are not made for glass surface so you won't see your art in bright colors. If you're asking if it comes easily if accidentally used on windows, then yes the can be swiped of with a wet towel.

Erasing in the sense of a correction rather not. You can wash out stains that appear in your clothes.

Unfortunately, the manufacturer does not specify this but can be contacted via the following link: https://www.crayola.com/help/

Yes, according to the description, these markers are also suitable for smooth surfaces.