Texture glitch, cheats glitch in 0.15.90.7

When I spawn the wither it's texture is glitched out and the beacon's beam texture is also glitched out. When I created a new world in creative I am still taking damage even in creative. When I tried to use it showed a message that cheats arent enabled even when I enabled the cheats. When I played in my old world I didn't have that problem. And I am unable to create a new world now to see if the problem still exists. Even in my old world when I go towards the spawn the have crashes. And I think the texture of the water with night vision and water breathing is a little glitched out. And the wither isn't attacking any other mobs. These are all the problems I noticed till now. I attached some screenshots. I am using a OnePlus x with 2.3GHz snapdragon 801 processor, adreno 330 GPU and 3gb of ram. If possible add gamerule keepinventory command in the full release.