The mobile map package version is set when the package is authored in ArcGIS Pro or when it is generated by the OfflineMapTask.
This property will be populated when you attempt to load the package. The version property will always be populated for you to examine, even if the package is an unsupported version.
ArcGIS Runtime SDKs currently support mobile map packages up to and including major version 4.
You may wish to check the version property before trying to access specific functionality. For example:
If the package fails to load, check that the version number has not exceeded the supported major version.