Maybe Phone/PC Overloaded.
Normal when CPU/RAM Overloaded
Try Restarting Pc 🙂
What Is This, Remove Your RP
When You Turn Off The Screen The Phone Goes To Sleep, Minecraft Also Goes to Sleep, Network I/O is Suspended So That's Normal 🙂
Sure Xbox/Pc Not Overloaded
Switch, Screenshot May Be Hard
Just Saying, Try Restarting Pc And Check If Ur Wifi Is Fine And Restart Router
Looks Like A Render Glitch
Could Be A Tiny Corruption/ Generation Error, Shouldn't Worry Too Much If You Want Make A New World
If You Really Need To See The Barriers Get A Texture Pack Which Gives Barriers A Texture, Be Sure To Remove The Pack When Distributing The Pack
Could Be Intentional