Yes, all the modes you mentioned are possible (as long as the game allows it).
In general everyone uses Microchip PICs to make their mods, so it makes sense to use their software (MPLAB) to help create and compile the code.
Once you have the software then you choose a programming language to write the code. The two choices with MPLAB are going to be C and Assembly.
With your language selected then you pretty much have to type out the code.
Jitter is pretty much just telling the controller to fire, change weapon, change weapon, (repeat).
DropShot is just pressing B when the RT is pulled.
QuickScope is Pulling in the LT, waiting a set amount of time, and then ulling the RT.
And Auto Aim is just pulling and releasing the LT really quickly over and over to exploit the aim-assist that is built into the game.
Your question was pretty broad, so I gave a broad answer. If you want to know more details about anything, feel free to ask.
