Job application question: What should I list as employment history?

Hi r/jobs! So I'm applying to a position at an organization I've technically worked/volunteered with and would like some others' insight on how to answer the questions in this application:

1. Have you worked with [this place] before?
2. Technically yes, technically no. I have been working on a project with them for 2 years, and for the first 6 months I received a stipend. Since then, I transitioned to a volunteer basis. I actually started as a volunteer as well so I didn't ever go through a hiring process nor am I in their system as an employee. Do you think I should put that I have been employed by them before?
3. Employment History, in general
4. The application has a form for Employment History, with tables for employer, dates employed, etc. As stated before, I can't figure out whether to list the previous gig/now volunteership as employment or not! I am inclined not to, as the application asks for three additional references other than direct supervisors of jobs held and I don't have many other references. I'd like to list my now-volunteer supervisor as one of those three additional references but not sure if that's unsavory.
5. Do you think I should also list an unpaid internship I did, which had a travel stipend, as employment as well?

I'm very confused and I'm worrying! Please comment with any thoughts, and I appreciate anybody reading. Thank you!

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