No, no, NO.
You can build <150 bricks in Demo Mode.
You can load any map, regardless.
You can have Add-Ons in Demo Mode.
You can click "Join A Game", then click "Query LAN" to join a LAN Game (If being hosted by an Unlocked version) in Demo Mode; this will give you unlimited bricks.
You cannot play Online in Demo Mode (Obviously).
You can load saves with over 150 bricks; it will only build the first 150 bricks that were planted in it. (By putting "Demo" infront of the save name)
You have the same Avatar Customization methods as the Unlocked version.
You must start with Demo Mode (Unless you bought the game before downloading).
You must have the Unlocked version for RTB to work.
You, sir, among most parts, are WRONG.