Samsung Galaxy A9 -Downgrade the original android 5.1.1 to 4.4? Is it possible?

As title~
Is it possible to downgrade the original existing android system 5.1.1 to 4.4?
I just bought the new phone and root it. But I found that some apps could not work well....
That's quite frustrating...
Hope that someone could help me~THANKS

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