Cut multiple videos and merge with ffmpeg

How can I cut a video into multiple parts and then join them together to make a new video with ffmpeg?

You question is quiet general...
The following example may help you, but it might not solve your specific issues.

The example applies three stages:

• Create synthetic video (with no audio):

  ffmpeg -f lavfi -i testsrc=duration=3:size=160x120:rate=10 -c:v rawvideo -pix_fmt rgb24 testsrc.avi
  

  (The created video is uncompressed).
  Reference: https://trac.ffmpeg.org/wiki/FilteringGuide

• Cut video into 3 parts (creating 3 video files):

  ffmpeg -i testsrc.avi -ss 00:00:00 -c copy -t 00:00:01 sec0.avi
  ffmpeg -i testsrc.avi -ss 00:00:01 -c copy -t 00:00:01 sec1.avi
  ffmpeg -i testsrc.avi -ss 00:00:02 -c copy -t 00:00:01 sec2.avi
  

  Reference: https://superuser.com/questions/138331/using-ffmpeg-to-cut-up-video

• Concatenate (merge) 3 parts in reverse order:

  ffmpeg -i "concat:sec2.avi|sec1.avi|sec0.avi" -codec copy output.avi
  

  Note: for Linux use single quotes '
  Reference: Concatenate two mp4 files using ffmpeg

Synthetic video looks as the following image: