Since multi-part archives are usually uploaded by the community, you can search for the full firmware set at these locations:
This site maintains a database of Official Micromax Stock Firmware for various Canvas models which can be used to update or restore devices. Download Micromax L50 CANVAS Software part04 rar
A reliable source for Micromax Stock ROMs and Flash Files that often hosts files on MediaFire or Mega. Since multi-part archives are usually uploaded by the
often requires checking dedicated firmware repositories or mobile repair forums, as official Micromax support for older models has significantly decreased. Where to Find Micromax Firmware Download Micromax L50 CANVAS Software part04 rar
Finding a specific multi-part RAR file like "part04" for the Micromax L50 Canvas