Two 3d printer marlin amendment

There are two marlin you need to amend. 1)I want to add more extruder to my 3d printer using CNC shield, please help me to amend the marlin to add the most number of extruder. As i know i can have e0e1e2e3e4e5. Can i have even more? Also teach me how to connect the wire from ramps1.4 to CNC shield and the a4988. I will use octoprint to test, please tell me how to configure multi exturder in octoprint. I will send you my marlin firmware. 2)I have a 3d printer, I want to upgrade my 3d printer firmware marlin to the latest marlin, I will send you my current marlin to you. You need to make a remark when there is any difference between my current marlin and the latest marlin with "rrr" so that I can know where you have amended. super easy job, right?