Download the official Lava V2s flash file, Stock ROM or Firmware
Marshmallow with Volte has been released for Lava V2s.
Lava V2s s208 (MarshMallow + Volte)
SP Flash Tool : Quick Points
Try to use Firmware Upgrade option to initialize Flashing.
While, loading Firmware in SP Flash tool.
Untick Preloader, which held responsible for Mobile life. If this file get corrupt, your Lava V2s will be dead.
Make sure to install Mtk driver to make communication between Mobile & PC (Flash tool)
While, installing Stock ROM. If the process get interrupted, it will result in Android logo with exclamation mark.