Peaceful mode doesn't work

I'm having an issue with peaceful mode I was on peaceful mode and I still saw mobs like Zombies,Creepers etc.

gatharian added (from MCPE-20991)
I'm having 2 different problems.

1. The game difficulty setting is not kept when you exit your world.
2. While in world, I cannot select the game difficulty "Hard" until I have selected the difficulties Normal or Easy first.

Steps to Reproduce

• Create a new world.
• Set the game difficulty to Peaceful.
• Create the world.
• While you're in the world change your game difficulty to Hard.
• You may not be able to select the game difficulty until you select Easy or Normal first.
• Once the game difficulty is set open the menu again.
• Notice that the game difficulty is correctly set to "Hard".
• Close your world.
• Edit your world.
• Notice the game difficulty is set to Peaceful again!