Great thread to start!
Different phones come with different built in software that may or may not allow for greater camera control. So to answer your question in short, it depends...
My basic model Samsung has limited camera control, and other apps just won't allow for expanded control.
My Oppo phone has much wider native control and third party apps do expand its capabilities.
One thing you might like to try on your phone is see if it has different camera control settings. For instance with the camera app on, swiping right should open up such a set of setting options, suchas Panorama, Pro, Auto, Hyperlapse, etc. The Pro function should give you greater exposure control, even if only limited.
Focus control can be achived by touching the screen of tghe phone. Start with focusing with your eye at the eyepiece and then adjusting the focus again when looking at the screen. What focuses for your eye will be different for the camera.
There are people producing remarkable images single frame & stacked using their phones.
Pic below of Saturn was taken right on opposition and the rings were showing the Seeliger Effect, which is why they are especially white. And of course I was using a smart phone adapter to hold the thing in place.
Oppo A5 2020, Pro function settings
Santel 9" f/13 Mak
7mm Vixen SSW eyepiece
Single frame, no post processing.
Alex.