How to convert .mp4 videos to .3gpp2 format.
Converting MPEG-4 Videos directly to 3GPP2 Multimedia Files (.mp4 to .3gpp2 conversion) is certainly possible and should be quite straightforward.
Try using one of many currently available video editing programs or conversion tools, such as the Movavi Video Converter, which allows users to import MP4 videos and export them in 3GPP2 format.
Video converting software