The total amount of energy always stays the same because of the law of conservation of energy, meaning that there is always the same amount of energy, it just gets turned into different forms like potential energy, kinetic energy, sound, thermal, etc.
Answer:
Part a)
Mass of m2 is given as

Part b)
Angular acceleration is given as

Part c)
Tension in the rope is given as

Explanation:
Part a)
When m1 and m2 both connected to the cylinder then the system is at rest
so we can use torque balance here




Part b)
When block m_2 is removed then system becomes unstable
so force equation of mass m1

also we have

now we have




so angular acceleration is given as



Part c)
Tension in the rope is given as



B. I think is the correct answer