Songs and Beginner Strumming

I’m a bit confused on Module 1 and 2 songs. Should you strum just on Beat 1 of each measure or strum on all 4 beats of the measure? The app makes it look like only Beat 1 but the strum section of these songs suggests all 4.

Welcome to the community Gil.
You start with just strumming on the first beat. Once you are
confident you can stay in time you can strum 1st and 3rd then
all 4 beats.
There is no good to be had strumming on all 4 beats if your chord
changes are up to par.