First, put the cross in the middle of your screen over what block you want to destroy. Left click, and be sure to hold it down. A crack animation will play. This will tell you how long it will take. There are certain blocks that take longer to destroy, and others that need tools such as pickaxes in order to get their materials. Bedrock is the only material you can't destroy. It is only found really deep down underground.
On creative just tap it. On survival or hardcore click and hold the block for about 4 secs and you get the block
Block it using any type of block :)
right click on the block in which you want to place the block
Do /give @p minecraft:command_block 64
press where you are going to put the block.
the piston can push 1 block long
IF you mean this as in you cant break a block just reinstall the game if you mean the block is broken and the item that comes from it is on the floor check if your inventory is full and get rid of some items also blocks stack up to 64
The Only thing That Can Break Obsidian Is A Diamond Pickaxe. :3
Nothing in vanilla aside from repeatedly hitting and creative mode can break obsidian. No amount of wither or TNT will break it.
You are unable to craft command blocks in minecraft, but if you have cheats enabled on your singleplayer world, you may type /give {player} minecraft:command_block
1 Block is a cubic metre, so 1km is 1,000 blocks.
you left click on them with any block or your fist and wait for it to break. -_-