1. Datablocks are used to store persistant, common information about a type of object. For example, all players using the default player type of PlayerStandardArmor have the same mass, movement speeds, jet properties, etc. Transmitting just means the server sending them to clients, so the clients have that information.
2. No. Javascript knowledge may help you with syntax, as they are similar. But you need a distinctly different language: torquescript.
3.in addition to what Resonte said, there is a torque script function named eval, which takes a string of code and executes it. There honestly isn't a whole lot of need for it, and you don't want to use it unless you fully understand what the risks of the function are.
4. No. It's similar to the javascript console in a browser, in that you can execute arbitrary lines of code. But it still only uses torque script.
5. See 3