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If you try to go back to an oreo based rom you might brick your device due to arb policy, so i would suggest to move any pie based rom. All the latest dev roms are arb4, hence try to avoid downgrading to older android version.
You can only move to latest pie based rom, as your device does not have pie based stable rom, i think it might brick your device. Hence i think you have to wait. Or you can contact any developer in this regard for proper info.