iPhone X software update availability

If it has already been updated to 16.7.10, it cannot be updated further.

last version 16.7.10

Exactly. iOS 16.7.10 was the last update for the iPhone X.

If you want to run iOS 17 or iOS 18, you will need a new phone.

The iPhone X cannot run iOS 17 or higher.

If there is ever an iOS 16.7.11 bug fix release, the iPhone X may be able to update to that. But whether there are any more iOS 16 updates or not, iOS 16 is, and will remain, the end of the line.