Yes, you can go out on a double. This is one of the most common and most contested variations. 🙂 As I've seen conflicting versions of the rules, I had to pick one.

No, double zeros are scored as zero.

• https://en.wikipedia.org/wiki/Mexican_Train#Variations
• https://www.mastersofgames.com/rules/mexican-train-dominoes-rules.htm
• https://www.mexicantrainfun.com/mexican-train-rules/

I thought it would be more fun if each game had a unique name to refer to. Since I'm trying to put a little joy in the world, why not a positive adjective combined with a cuddly animal?