Hi,
Have you performed these changes on your Development Server first.If you performed on DEV then from there you can transport these to QTY as well as on PRD finally.
For licensing concern if you've only one developer user license & which you implemented on your DEV server for the customizations & testings etc,than as per SAP licensing you can maintain/register Developer on only one server if you've only one user license.During audit period SAP Audit team will ask you to send developer details as well as system details on which you are performing developments.
On your landscape you can create developer user on QTY as well as on PRD but you can't register this user as developer on QTY & PRD (This will surely be a licensing issue during SAP Audit).
There should be only one developer on your landscape who authorizes for developments.So as per my suggestions don't register any other developer on any other landscape system apart from the development(If you've only one developer user license) .For the required changes or testing please follow SAP standard flow i.e from DEV ---> QTY ---> PRD.
Hope you found this information useful.Please correct if 'm wrong.
Thanks,
Gaurav