Looking to nail down what counts as a cover. What if an artist releases the same song in several different languages (e.g. Czech, German and English). Is each considered a separate cover?
Yes, they would be separate covers, assuming they are covers of a song originally done by someone else. They would actually be covers of different adaptations (each translation is a separate adaptation).
If the song is an original that the artist records in several languages, then it's a bit more complicated. For example, Kraftwerk released several of their songs in English and German. We would not enter one of these songs just to record Kraftwerk's German and English versions. But as soon as someone else records one of those languages, then we can get started. To be honest I don't remember the precise details: if someone covers the German version I don't remember if we would enter the English version as well, or wait until someone covers that one. We would consider the German version (artist's home language) as the original (assuming they were released at the same time, which I believe is the case with Kraftwerk).
What if an artist covers the same song in the same language, but using two different adaptions. Is each considered a different cover?
I presume you mean in separate performances, not changing adaptation in the middle of a song It depends really what the adaptations are. We don't consider different arrangements to be adaptations, so in that case no, they wouldn't be different covers. If they really are different adaptations (i.e. different words or different tunes) then yes we probably would consider them to be different covers (or a medley if the adaptation changes in the middle of a song, it does happen, occasionally... ).