If it's a youtube video it can be done with the , and . keys, which move the video forwards and backwards by 1 frame. If it's another type of video I don't know.

Most runs in a 8 level category will have all runs driven first try anyway I think.

Counting the time on that level from the first frame on which that level is visible would be the best I think.

Currently the star animations count in the total time and you need a certain version of bike race to be able to skip it.

A run I had before I knew about this was beaten by 7 seconds by a run that skipped the animations, while the sum of those times was 5 seconds slower than the sum of mine. This means that the individual times don't matter at all anymore, the only thing that matters is how fast you can press next level.

Even if I were to use that specific version of bike race, how fast I can click would still have a major influence on how good the run is, and I don't think being able to click fast should be a skill that is required to get good bike race speedruns.

This would only work if all runs were driven in the first attempt, so it should probably only apply in the 8 level categories.