Karbonn S5(a21) Titanium Hard Reset 100% Done tested by me

Press and hold VOLUME UP + POWER KEY

now you see green screen don't release volume up key

after 10 seconds you see red screen, now release Volume up key.

now you see recovery options.

select wipe data with factory reset and press power key for 2 sec.

now select yes -- delete all user data and press power key for 2 second.

now reboot device