Please help me figure this out.

What is the currently best-developed and stable SailfishOS version?
From what I can see, it's SailfishX (is that the same as Sailfish 3?), and the list of devices is small:
Sony Xperia™ 10 and Xperia™ 10 Plus, Sony Xperia™ XA2 product variants, Sony Xperia™ X, and Gemini PDA.
(source)
Am I correct?
Are there any outstanding community contributions for other hardware I should be aware of?

Where can I look up development status and official statements?
The blog gives the impression of moderate but continuous activity?
Any sort of slightly more technical news? Open Source repositories to look at?
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I guess these are my general questions.

More specifically:
I could get my hands on an Intex Aquafish for ~75€, tomorrow.
It currently has Sailfish 2.0 installed.
Apparently it can be updated to Sailfish 3.something.
Is that a current version of SailfishOS? Again, is Sailfish 3.x the same as SailfishX???

I suppose a self-upgraded version will not include Android support?

If I buy the license, will it be transferable to any new device I choose to buy? Is it a lifetime License?
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Is installing SailfishOS on one of the supported devices a smooth and pain-free experience, and can I expect an "everything works ootb experience" after that?

Thanks.