Wish I remembered the whole story but it was some feature of the original Chess Mentor before Erik bought it, streamlined the GUI, and more than doubled content. So no, I don't think the variations are still available but I'm often wrong. 
Here's another:
http://www.chess.com/forum/view/chess-mentor/variation
Thank you for your reply. Would chess.com be open to having a volunteer rationalize the Mentor problem-set names?
Hi, I am a premium member and i have sent the same question exactly to the Support Team 3 days ago and was notified that someone will reply to me within 24 hours, but no one has replied yet. I also see here no one from chess.com has answered this question asked year and a half ago!
I think that the site just grew so fast that they can't keep up.
in the course Endings, Openings, A taste of the middle, several of the lessons refer to other "variations" of the current lesson, but there is no obvious indication of which lesson title contains which variation! For example: Lesson EOT127, Basic Diagonal Oppostion' refers the student to "Variation One", but none of the lessons include "Variation One", or V1, etc in either the title or the text. Is there a simple way to find those cited lesson variations?
Variations were exclusive to the original Chess mentor software. You could be on a lesson, and click on Variation if you wanted. The Chess mentor on chess.com has a lot more content, but the variation feature is missing.
in the course Endings, Openings, A taste of the middle, several of the lessons refer to other "variations" of the current lesson, but there is no obvious indication of which lesson title contains which variation! For example: Lesson EOT127, Basic Diagonal Oppostion' refers the student to "Variation One", but none of the lessons include "Variation One", or V1, etc in either the title or the text. Is there a simple way to find those cited lesson variations?