ASUS - ZenTalk

sir my laptop model is ASUS VIVOBOOK 15 X540UA ,but in bios it shows X540UAR why sir ,please tell sir ,i was google it ,but didnt get the answer,ur expert so reply sir

thanks for ur reply sir

sir does my laptop support dual channel memory ,my laptop ram is 4gb ddr4 soddim ,can i upgrade single 8gb . laptop SL no ,K4N0GR01U67614B

sir my laptop shows it has pcie gen 3.0 x4 2.5ghz ,what does it means,does it has m.2 slot

Thanks for ur responce sir