> Is it possible at this point to simply open-source your software to accelerate the development of the product and later on close source it, or some kind of arrangement where you allow others to partake but still retain ownership of the software?

Yes, this is possible, but you have to make sure all contributors abstain from their rights - which can actually be a reason for potential contributors not to participate. If you want free work from other devs, you usually need to give them something in return for this, which means usually the source code of the whole product. They may not be happy with the idea of giving you some source code for free, and then you close the source and sell their work. Note you can never close an already published version of the source afterwards, once you made a version of your product FOSS, that version stays open. Only newer versions can become closed. That means, closing afterwards the source will only cut external contributors from updates.

> Is it possible here to limit the use of your technology to private actors, educational institutions and non-profits while demanding royalty/license fees from businesses that wish to license your tech for use in their non-profit ventures?

Absolutely (though your software then is not FOSS software) - but this question is not about open source, and the answer "yes" is valid for closed or open source equally. If you can enforce correct licensing for commercial usage, especially internal usage inside a company, is a complete different thing. GPL, for example, does not even try to enforce this, that license only enforces depending code (derivative works) to be open-sourced in case of public deployment.

> At this point is it possible to enforce a clause that would prevent the future owner from shutting down and wiping the technology from public use?

You can surely write such a clause into the selling contract, or you can release the code to the public under a suitable open-source licence right before the sale. If you can *enforce* such a clause is a different question, that may require to be tested in court.