Yes, add as many as you need to.
The FAQ content tool is a special tool that will create expandable and collapsible FAQ sections in your content. When editing an FAQ section you can enter a question/answer pair:

When shown in your article, it is shown collapsed, but it can be toggled open:
Yes, add as many as you need to.
Using the tune menu in the editor you can configure the heading level of the FAQ section. It defaults to h2.
When the HTML is emitted for FAQs, HelpGuides will automatically include the LD-JSON for search engines and GPTs to more easily understand the content: