A:Answer Yes, A51 has multiwindow/Dual window.
Be in the app you want to dual window with, You swipe up for your Tabs/Home/Back buttons, tap Tabs, then tap and hold the icon of the next app you want to have in dual window, then tap "Open In Split-Screen View" or "Open In Pop-up view".
You can also lock apps, and change app aspect ratios in this screen.