You can do this in the real Minecraft in creative.
This most likely isnt a bug. Maybe the dev's wanted this...
Look at what device it says. It says iPad 2 - that is not android. I am telling Johan that it isn't available on iOS. I'm not bothered about android...
When in water, creeper and TNT explosions do not effect any blocks around them. This is not a bug. This is how TNT cannons are made.
Dig up the hoed dirt block for now until it is fixed. The seeds should be there.