Technically it is, you just need to turn dev mode on so you can install apps from .apk(android package) files.
Note that the process will factory reset the data on your chromebook though, so be sure to back up your shit if you do that lol. Also, from personal experience, every subsequent time you turn your chromebook on, it will make a loud beeping sound you can't lower the volume of, so be mindful of that if you go through with it.
(Not gonna say how, just look it up.)
No lmao.
I just know this from having a Chromebook myself and going down the whole "Chromebooks are android devices" rabbit-hole myself.
Adding onto what I said before, Chromebooks are essentially android tablets with a keyboard, and Google disables the usage of .apk files for user-safety reasons(unlike literally every other android), but that's where dev mode comes in.
afaik, There is no possible way that I know of to install a non play store app onto a Chromebook outside of dev mode. Google just hates fun. :P
