Africa is separate from Asia, no? (especially after the Suez canal was digged-Ferdinand de Lesseps, doing the same in Panama-to split North and South America).

That's like saying England isn't island because of the tunnel. Poetically, fine.
But building canel shouldn't make a continent. But point is speaking about the various continents doesn't make much sense, either. Why not label according tectonic plates? [because it would be geekly silly- we name things because of custom, such as things like "shooting stars"- how grossly wrong can you get?].
I say a body that orbits a sun is a planet- binary planets are when planets are say within 50% of the mass of each other. The distinction that we are worrying about is between major planets and minor planets. One definition of a major planet might be that it's likely to stay in orbit and not be destroyed within a couple billion years [and therefore Mercury, Venus and Earth aren't planets:)]