I've been asked if I can check some faulty behavior of a device, a cheap Chinese android smartphone.

I'm not really an android expert, usually I install a few apps to help me figure out few things about the device (if it's relevant or interesting let me know if it's possible to list what apps I used). These apps I've reported conflicting results compared to what was displayed in the main android settings area:

- Storage 16gb vs 3.9gb in app report
- Android version 9.0 but API level 23 (Android 6) in app report

This kinda reminds me of fake USB thumb drives scams with less memory than advertised.

So is there a way (preferably without root) to test/analyze common technical details of a device? 

Like
- Storage
- Android version
- RAM
- CPU
- Something else that can be spoofed?

FLOSS solutions are highly appreciated! :)