Just so you know the prefered version is meant to be used on construction and imply's it is not a guarenteed change to the back buffer hence the name it is a hint.
Once you have intialized the graphics device basically by the time you are in load or when the game is running.
you can alternately call.
you must then call ApplyChanges() for the above ...
Technically the above is meant to be used in concert with one of the existing display modes Width Height found from a list of support display modes queryed thru the below function.
or thru the CurrentAdapter
if you have the hardware switch on that is.
If you go into full screen via hardware mode = true i.e. you really change mode in order to ensure you have a true hd mode running and not do a windowed fs in the case you are doing fake full screen then you are using the users CurrentDisplayMode
Not sure how that relates in android resolution wise to be honest as android is probably somewhat different but on pc's.
Then if that is not a valid (supported) Display mode resolution, preffered wont do a switch then you will again have the problem were the mouse and even the display is improperly matched up to the monitor resolution.
A valid display mode also includes matching the aspect ratio color format and refresh rate but you really only need to worry about the w h and aspect to do a switch.
That can be set by preffered at the start but again it must match a users supported display mode in order to do so if the intention is to ensure a true hd DisplayMode is switched to.
Im pretty sure the viewport can be changed as well but i forget how to do it.
Here is the last mode testing app i made its for windows gl desktop but it works on dx too i have no idea if you can port this over to your android app as i never tried but its really just straight up monogame class files and a font, maybe it will help.
Hitting f10 after you run this app will put you in fullscreen hitting f9 subsequently will do actual hardware mode switches thru your available supported display modes at least on pc this method calls a search function to match the requested w h to the closest supported display mode, to do so.