Not sure, we're going to have to check the first two with our software team.
That said, the Almond+ does run OpenWRT, so for Radius, it should be possible.
As for the last question, can you please expand, as without the stock firmware, you wouldn't be able to boot the Almond+, but if you mean if it'll be possible if it'll be possible to run third party software on the Almond+, then the answer is yes.