Hi,
1. We don't know. No one reported a problem with it so far.
2. We have other users using rockettheme templates and it's working great.
3. You can post on the forum your questions. A lot has already been answered on the forum so you might want to search a bit before posting
4. Yes. When you create a menu or a module to display content with HikaShop, you can access the HikaShop options with a link on the right panel of the menu/module edition screen. One of the options of the HikaShop options will be the number of columns that you can set independently between the listing of categories menu and the products listing module associated with that menu.
5. Yes. You can see it on our demo website.
6. No. You get a 1 year support via email. We will put in place an extension of support on our website during this year for people wanting to extend it. The price will of course be a lot lower than HikaShop itself.