Don't know if this is still relevant to you, but I will explain it anyway. Also I don't know your experience level, so I will go rather detailed. There are some variants of this fork. Some have two steel springs inside some have a spring and a dampener (the part you indicated), but both tubes should be populated by either of the two. A dampener basically is used for slowing down the speed that the spring contracts and extends with, e.g. through increased friction or flow of a liquid through a tiny opening (there are many ways to achieve this, some rather simple, others more complex). It also takes energy out of the system, which means if your spring was oscillating, with each oscillation the dampener would take out a bit of energy and translate it to heat, making the next oscillation cycle a little shorter in length. <So a part missing from the fork is rather odd. Did you buy it used or new?> Actually on suntour's webiste you can find the construction plans of those forks including the part numbers of individual parts. Make sure that the name of your fork matches with the name of the fork specified in the document. Be careful: a comma used in the name in the document might indicate that the document specifies 2 slightly different forks. e.g. the document for the "SF16-XCT-DS-HLO-29-80,100" specifies two similar forks with 80mm travel on one and 100mm travel on the other fork, thus the name of your exact fork will either end on 80 or 100, but not both, eg: SF16 XCT DS HLO 29 T 100 (that's what might be written on the fork somewhere). Variations in the parts can depend on the exact model of the fork, the wheel size... For the fork named above, intended for a 29 inch wheel, the number for the dampener would be FUN050-14 (don't ask me how they came up with that part number😂). The parts can be found online for sale.

If you’re talking about mt200 shimano hydraulic brakes, then yes, that’s what I have on this fork

It helps to prime the filter so it’s not dry when the engine starts allowing you to reduce risk of lower oil levels from changing oil.

You absolutely need to add some new oil to the rubber gasket of the filter so that it makes a proper seal with the oil filter housing’s metal surface. Adding oil to the filter’s canister is not necessary (and not even possible when a car has a horizontal mount vs. this vertical one) IF you cycle the key to on for 3-4 seconds, then off, then repeat a couple more times. This will activate the oil pump a few times to prime the oil lines and help protect the engine during the first start up after losing all its lubrication.