Could anyone help me with test number 3?
I am having WA for some time and can't figure out what seems to be the problem.

I had WA #3 for silly mistake on 'lazy' calculation. remember, new lazy of a node is added to previous lazy, not replaces :) again, if u calculate sum immediately, then only new lazy adds to sum not new+prev. i do not know your method. but, these were my mistakes.