“Single-event” might also be translated by mono-événement but it would help if you tell more about the context.

“Multi-event mobile application” can be *Application mobile multi-événement“

Depending on the context, if you’re talking about software that are multi-threaded or not, you could use :

Exécution Séquentielle which means the program can only execute one operation at a time.

Exécution Parallèles which means the program does handle multiple operation at a time.

To answer your specific translation request : multi-event mobile application could be said :

“Application mobile parallélisée”

As multi-threaded programs tends to be used to simulate real-time reactions to inputs, you could also say

“Application mobile en temps réel”