Ignoring fail's "reply", which has nothing to do with the question: if you want to preserve input from later levels, one way is to use
TAS Movie Editor to copy the input from one movie file and paste it into another. You would make a copy of your movie, note the frame range you want to copy, redo the error in one of the files, and copy the frame range from the other movie.
Be warned that there is a high chance of desyncs due to lag differences; a good way to reduce them is to copy in-level input. For example, you copy the input starting from the first frame in which the game timer runs in a zone, and paste it so that it becomes the first frame, adding blank frames until you are pasting in such a place.
Even then, many levels don't help at all — any changes before DDZ, DEZ1, DEZ2, SSZ or LRZ1 will almost always cause these levels to desync at the boss. Likewise, changes before SOZ2 may cause a desync if you rely on the ghosts behaving in a certain way. Changes before MHZ1 can cause a desync at the boss as well because the flame on/off pattern is different. Changes before either CNZ1 or CNZ2 are almost certain to desync everywhere because of the balloons ending up in different positions. Changes before MGZ2 can cause Knuckles' boss to desync due to a different pattern, and changes before MGZ1 can cause lag differences if beating Sonic's MHZ2 boss in act 1, leading to a desync. All of these can be worked around, but it takes time and effort.
