I have a basic question about Quartus tcl command "get_fanins". so I noticed that there are many options for this command and I'm confused which option should I use?

What u can do is use the tecnology map viewer to look into the netlist.

-asynch Traverse through asynch edges, this normal happened on after LUT1 where no clock involve.

-synch Traverse through synch edges, usually, on the register where clock is involve.

-clock Traverse through clock edges, on the clock path rather than the data path. for example, output of PLL.