Flashing manually is a complex process. It requires installing specific VCOM/Preloader drivers and carefully selecting the "scatter file" within the extracted ROM folder.
Files hosted on enthusiast forums like Hovatek or HardReset.info are generally official stock ROMs but should be verified for the exact hardware version to avoid permanent bricking. Download MICROMAX L50CANVAS Firmware USB part13 rar
Based on typical experiences with similar Micromax stock ROMs and firmware flashing procedures, here is a general assessment of what to expect: Flashing manually is a complex process