For Android devices, updates are controlled by several parties and aren’t guaranteed to be released for all models at the same time.
Most manufacturers will guarantee at least 2 years of software updates from the initial release of the device; however, when those updates are pushed depends on several factors. Another thing to keep in mind is that just because a major version of Android is available (i.e.: Android 11) when a phone is released, it doesn’t mean that the phone will come with the latest version or be compatible for that update at the time of release.
The good news is that app compatibility is not directly tied to Android version, meaning phones sold on Back Market will provide access to all of your favorite apps for years to come.
If you can’t find the specs you’re looking for, you can try searching for the device on these sites:
For Android, Windows: https://www.kimovil.com/en/