Edit functions could be done with or without time code. Time code makes these functions frame accurate. Without it, you must depend on control track which is like the VTR counting the pulses of the frames passing. The problem with control track editing is that the VTRs don't count it perfectly. If you make several previews or passes at your edit, this error may compound.
Time code identifies each frame with a unique and sequential number.
Usually, allows for frame accurate editing time after time. As for single frame recording, time code is essential because if you edited with control track your typical error of 2 frames is greater than the amount of material you want to record at any one time, which is only one frame. Without time code, the results would be disasterous. But I am still very fuzzy about what time code really is. There is no point that I can think of to pre-black a tape and then record over it with a camera.