> by definition Basic Income is unconditional. Anyone who applies should get it.

Doesn't have to be. Some versions are, some aren't. Given we are talking about a system that does not exist, not sure why you say it is one thing or the other. Some versions give to minors, some do not. Some only give to citizens in good standing (no felons). Conditions can exist and should exist in my opinion.

And what if a dolphin applies? Perhaps deputised by someone?

This means, there's at least one condition: only humans can apply.

That's not citizenship, that's residency. Those are two different things with very different implications as to your status in a country which can also vary depending on the length of residency.