First install V5 (it will not touch your V4 setup), then use Database Backup module on V4 and V5 to upgrade as described in this topic:
Note you don’t need to buy Database Backup module for V4 - it will work in trial mode to allow you to do the upgrade.
After upgrading, in V5, go to Manage > Settings > Program Settings > Maintenance, click “Update old rules”.
That is all you need to do. Everything should be transferred across successfully.
In Manage > Users > Roles, select the specific Role, then uncheck “Can change report date filter” and “can display old tickets”. That should do it.
One improvement that comes to mind is V5 handles dropped database connections better, so if you lose wireless connection while SambaPOS is open, in V4 it would likely freeze, but in V5 it will show a dialog giving you the option to retry the connection.