The required energy depends on flag mass, gravitational acceleration and pole height. Raising it slowly or quickly does not change the work done. Doubling the lifting speed halves the time, doubling the required power.
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Lifting to the 20th floor requires twice the energy because the vertical height is doubled. However, since the time taken is also doubled, the power required remains exactly the same as before.
The gain in potential energy is 36250 joules in both cases, calculated by multiplying mass, gravity and height. Gravitational potential energy depends only on vertical height and is completely independent of the path taken.
The transformations are chemical to kinetic and potential, potential to kinetic, light to chemical, potential to kinetic, chemical to thermal and light, chemical to sound and light, sound to electrical, electrical to light and light to electrical.
Statements (iii) and (iv) are correct. At the highest peak, vertical velocity momentarily becomes zero making kinetic energy zero, while the entire initial mechanical energy turns into maximum gravitational potential energy at that height.