Since R610 is supported from 9.13.x code you can't downgrade it. You can check below link which will take you to ZD document and you can validate in release note of 9.13 version about the supported AP model. You can then compare all your existing AP model are supported in which code and accordingly decide to upgrade.
There are certain images/File available only for Premium User (one who has active/valid support contract). You also need an active support on controller to upgrade it so I would suggest to check your controller active support via Ruckus admin team.