Question

is the melting point and freezing point of water is same and why water exists as ice as well as water at 0 celcius

Answer 1

Freezing point and melting point water is same that is 0$°$C.
This is so because during a phase change that is from solid to liquid or vice versa some amount of latent heat energy (hidden heat energy) is required. This cannot be measured by thermometers. To convert ice into water, the latent heat should be added and to convert water into ice, latent heat should be removed to break or make the molecular bonding respectively. Hence the phase change occurs at same temperature.