1) When you create and submit a request in the request area, via a request queue, please note that the request queue itself is ALSO a project. Therefore if there is no other project specified, the submitted request lands in the request queue. For best practice, I advise my users to specify a different project, so that the queue configuration doesn't conflict with the intake team's needs.
Requests and issues are almost the same thing. And yes, they will all be stored in the issues tab. I landed on the following instruction for my own users: "Requests and issues are the same thing and are named differently based on the two locations Workfront has for you to submit these items. If you're reading Adobe documentation a "request" is submitted through the requests area. An "issue" is submitted straight from a project's "issues" section and is related to that specific project. You can refer to either interchangeably, as a request or an issue and most users will know what you're referring to." This works for my company because we're using the same exact queue topics in both a request queue and a project and I don't want them to be confused about why we do that.
2) it will be converted to one task
3) It is configured to map back to the original issue by default. You should check your setup area to ensure you didn't change this. It's under Project Preferences, in the Tasks and Issues section.
4) You should convert your issue to a Project and fill it with your multiple tasks.
5) You should click on each field in the custom form (in the setup area), and indicate whether it is mandatory. It is optional by default, so nothing to do here.