the iron iron carbide phase diagram does not have a single microstructure, it has different microstructures depending on the carbon content of the steel.

At room temperature iron is a lustrous metallic gray colour.

actually there is no difference in beta phase and alpha phase when we talk about crystal structure of iron.

beta phase has the same structure as the alpha phase. the olny difference is the magnetic properties which are absent in beta phase due to the expanded lattice parameter.

Pretty sure it is ferrite

to know what will be the crystal structure and physiacal and chemical properties of iron at known carbon percentage and temperature. provided that slow and uniform cooling rate is there and no quenching.