[q] alps sm-g900h mtk6589 laggy phone topic

Hi all,

Can I replace the ROM of my phone to earlier versions?
The manufactures have done a mod of JB 4.2 to 4.4 KitKat but the ROM have a lot of bugs, sad :( , my question is, can I flash a 4.2.x stable ROM from for example a S4 clone ROM? Plus, my download mode is fake because everything is chinese.
And also, with the attachments and using CPU-Z.

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