Almost everyday that I am using my OctoPrint, I refer to this page which includes all the GCODE commands. It would be good to read a little of that to understand how simple these toolpath commands are at the heart of what's going on.
Terminal tab, you could toggle off the display for things like temperature so that it's not so busy. Then enter
M115 and read the response. The page suggested above describes that as "M115: Get Firmware Version and Capabilities". So if anyone asks you about your firmware version, that's the fastest way to get the response.
M104 and understand the difference. One will set the hotend temperature (in Celsius) and the other will do the same thing, only it will wait until it gets there. We call that "blocking" meaning that it won't accept anything else to do until it completes that task.
Find a small
gcode file and open it up on your workstation in a text editor. Read the top 30 lines and lookup those commands. It's important to understand what
relative modes mean. Absolute means that I could tell the assembly to move to a certain X/Y position. Relative means that I could tell the assembly to move over a certain amount from where it was a moment ago.
Read this troubleshooting guide for some how-to's with respect to a Raspberry Pi, remoting in and such. Look for "Remote in with SSH", for example.
I buy books. I have the O'Reilly "Raspberry Pi Cookbook" and "Bash Pocket Reference", Wiley's "Learning Python with Raspberry Pi".
There are the OctoPrint docs as well.