Offbrand Android states one OS but shows another in linked apps

I recently bought a generic 10" tablet by E-CrossStu that stated it is on Android 11 with 512GB storage with 4GB RAM. I thought this is a great deal for $100. I am now going through trying to add the apps I use and many say "incompatible with OS version" or just don't show up in the Play Store at all. I thought this can't be right if it's Android 11. Then I get emails from Gmail and Amazon trying to confirm that it is me signing in from a different device stating the sign-ins are from an Android 5.1 tablet. Did I just get duped? I cannot find ANYTHING on the web regarding this happening to others. In the tablet settings, it does state Android 11 with specs advertised. When I try System Update, Software Updates, or Wireless Updates, it just goes to the About Tablet page which states: - Android 11 - Model # & Custom Build: TAB910 - Baseband Version: MOLY.WR8.W1449.MD.WG.MP.V16 - CPU: 10cores2.3GHz - Kernel: 3.10.72 root@twd-PowerEdge-R720xd - Build Number: K1008P95_V1.0.3_211119. And None of those lines can be opened to get further settings. I am just confused and think my device has some fake information locked into it somehow so I'm not really getting what it states even in the System Settings...and I'm a little concerned about privacy/security if that is something that can really be done... Any thoughts?