[VLM]

For android, get good at handling null everywhere in everything checking all the time now, or learn it the hard way later. You'll be spending lots of time tracking down "wait, how could that have ever possibly returned a null?"

Ditto async and observer and livedata type stuff. Never move data between things any way other than async. MVVM and all that, with caching repositories and stuff.

Architecture changes fast enough that you have to be careful not to waste time and effort supporting some ancient version and NIH writing your own implementations of stuff that's newly added in current versions. Yet if you try to ship using cool alpha quality features, that's a whole different headache. For extra fun you can end up with both problems at the same time in different parts of the app.