Reverse video frames with std.Reverse

import vapoursynth as vs
import havsfunc as haf
import muvsfunc as muvs
import mvsfunc as mvs
import descale as descale
import G41Fun as fun
core = vs.get_core()

video = core.lsmas.LWLibavSource(source=r'video_cut\cut.mkv')

video = core.std.Trim(video, 19, 28)
video = core.std.Reverse(video)

video = core.fmtc.resample(video, css="444")
video = descale.Debilinear(video, 718,404)

video = core.std.CropRel(video, left=84, top=52, right=94, bottom=48)

video = core.fmtc.bitdepth(video, bits=16)
video.set_output()

You can also add the reverse one to the original and create this effect:

import vapoursynth as vs
import havsfunc as haf
import muvsfunc as muvs
import mvsfunc as mvs
import descale as descale
import G41Fun as fun
core = vs.get_core()

video = core.lsmas.LWLibavSource(source=r'video_cut\cut.mkv')

video1 = core.std.Trim(video, 19, 28) # frames we want
video2 = core.std.Trim(video, 20, 27) # frames we want to reverse
video2 = core.std.Reverse(video2)
video = video1 + video2 # we add both into a single clip

video = core.fmtc.resample(video, css="444")
video = descale.Debilinear(video, 718,404)

video = core.std.CropRel(video, left=84, top=52, right=94, bottom=48)

video = core.fmtc.bitdepth(video, bits=16)
video.set_output()