Howdy Howdy! I've been doing Jams for long enough to understand how they generally work, so I think I'll be able to answer your questions.
1. For this specific Jam, there is no mention of working in groups, so technically you could work with another on your submission. However this Jam is focused, or at least it is to me, on how you, yes, you interpret the theme and if you stuck to it, and with this being a re-occurring Jam, it's also about how you improve over time. So I would recommend you work solo. However, that doesn't mean you can't have someone else have a listen and help you get things right! Feel free to share the current state of your submission on the Weekly Note Discord Server, or with others who could help you fix things. As long as it's not AI assistance, you're all good to go!
2. Correct! The theme of a Jam is generally always revealed right as it officially begins.
3. Absolutely! There is only one rule that restricts what you make, and that's the No-AI rule (Generative AI). Other than that, you're free to make what you please as long as it sticks to the theme, loops, one shots, you name it! We're here to hear (ahah) what your and many other creative minds come up with.
Sorry that this is being written literally half an hour away from when the Jam starts, hope I get to hear something made by you!