Unfortunately you can't downgrade. As 4.2.2 was on the old bootloader. As I suggested boot into download mode, volume down and power button and see if there is a knox counter. If it says knox you have the new bootloader. If there is no reference to KNOX at all then you can safely install stock 4.2.2.
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Phone: Samsung Galaxy S4 I9505
Rom: DjeMBeY XXUFNC9 4.4.2 | Der Kernel: KT Kernel | Theme: Domination V2.0
Tablet: Nexus 7 2013 32GB
Rom: OmniRom 4.4.2 | Der Kernel: Stock Omni
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