Add-on creation rules for JavaScript item

I recently uploaded this: RasterPro - Halftone Image Generator
The idea is to create add-ons to it: additional pattern sets, animation effects, interactivity, visual editors, etc.
My questions are:

  1. Can I create add-on as separate item that requires the main item purchasing?
  2. Can I upload add-on in the same category as the main item? If not, which category is suitable for this?
  3. Are there any specific rules for creating such add-ons for JavaScript category?
  1. yes you can create add-ons as a separate item but personally I think to make your existing Item more reliable you should to merge all add-ons with that item
  2. yes you can upload in the same category but your add-ons and the category should be relative
  3. no such specific rules there but qulaity standard first.

Thank you!