Hello, I'll answer your questions below.
1. The plugin doesn't require any comment like <parameter: 1:2....> in order to run anything. While there are support for comments, they're very short and easy to remember and are completely optional, such as <passive: common event name>, which does the same job as the command "Call Common Event" in parallel. Most of other comments are user-setup, which mean you create your own system and your own comment, something like <haha> or <hoho>.
2. Yes, you can use it to create simpler game. You can check out the Showcase page to see what other users have been cooking with it.
3. Side Scrolling combat is possible if they're more like Little Fighter 2 and not like Megaman with a lot of jumping and platforming. Basically, Beat 'em up is possible.