HTC 816G downgrade from lolipop to kitkat

hi
i had to root my htc 816g after the lollipop update cuz the small internal memory size and i couldn't even update the soft apps
i used TWRP
i just want to downgrade it to kitkat with the right steps and the right stock
i want to be able to apply the official updates too so can i or i will never be able to since i rooted it before ?!
i don't have enough info about rooting or backing up so pls try to explain

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Downgrade from MM to Stock

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