How do I get updates on past updates such as the snakes one?

Answer 1

If you mean how do you get past updates, you can't. Events are time based and are only available for a month and a bit usually. They do not come back after they finish. The content from it may return in the future under a new version of the same update but all the mechanics will not be the same.

Answer 2

You visit your store for apps and downloading an update for the game.