The Meaning of Life, the Universe, and Everything.
Currently, the canPlaceOn nbt tag will not allow the block to be placed on anything when you don't specify it. This means that if you would like to only limit placement of certain blocks, you need to add EVERY SINGLE BLOCK to the canPlaceOn tag for the blocks you want to act normally. This is extremely inconvenient. My suggestion is to have an unspecified tag specify to be placed on anything and a tag of an empty list ("") to specify nothing.
Rollback Post to RevisionRollBack
Remember those versions that minecraft pranked us with? Specifically:
Those are still downloadable! Watch this video for 2.0:
To download the other ones you need to make a folder in the versions folder for minecraft and put the client and JSON file for the versions in there. They all need to be named the same aside from file extensions. Once you do that, you will be able to choose that version when making a new profile with the minecraft launcher.