Question about Creality K1C

You can, but you don't have to. It works quite well without. I have also used 3DLac for tall objects with a small footprint, and traces can be easily removed afterwards.

I print pla without ever using adhesive, which is not necessary for this material. It all depends on the filament you use

I used adhesive spray on the K1c. The best adhesive spray, in my experience, is 3DLac.