This goes to both the development and final versions of the arduboy, as I would like to know how many games I could have on the device at one time
I think the most games I’ve seen on a unit is in Atomic’s Puzzle Pack.
For this version of the Arduboy Library, which is modified and included in the source locally, we see Atomic is
using 28,648 of 28,672 bytes. It’s pretty cool to see that many games on a unit.
We can also see how Atomic runs each game in the accompanying source.
You can only load one sketch at a time. If that single sketch is written to let you play different games that have been coded within it, as with Atomic Puzzle Pack that @ekem mentioned, then you can get the equivalent of multiple games (note the word “Pack” in the name).
However, you can’t pick two or more different sketches and load them up at the same time, and select between them.