1. Summation of torque = 0. Do not use other different definition.
Summation of force = 0 , not restricted to upward and downward force only. The resultant force at B is not needed , only component form required, hence to the left and upwards direction required. Many gave strange angles.
2. The mistake of not converting T to kelvin
3. (iii)The change of state and rise in temperature of water would be detected if proper diagram is included.
(iv)The mass of ice that has been converted to water can easily be missed out even by good students.The part is a continuation of (iii)
