We can't reliably manage stutter by rehearsing like that. Speaking with others is a different mode of communication performance than speaking on our own, or speaking to an app. However, speaking with someone online might help you get used to being in a stressful situation (that of speaking to someone in general, I mean). It's not certain, though. You could try speech therapy to address your stutter directly instead. This is going to have a different impact than simply rehearsing speech, because a stutter is not simply a lack of training.