Explain why iron (Fr) can exist in two stable oxidation states. And state which of the two state is more stable form.?

Iron ....oxidation states

Iron has two common oxidation states: +2 and +3, as in FeO and Fe2O3. When iron metal undergoes oxidation it will wind up as Fe2O3, potentially making Fe(III) the more stable oxidation state.

A vast, but common, oversimplification revolves around the valence electrons of iron which are found in the 3d and 4s.

Fe ........ [Ar] 3d6, 4s2

Fe2+..... [Ar] 3d6 ... two electrons are paired in the 3d, some repulsion

Fe3+ .... [Ar] 3d5 ... each electron occupies "its own" orbital, minimum repulsion.

This refers more to the free ions of iron rather than to their oxidation states in compounds. This is because there are no discrete ions of iron in iron compounds. The bonds between iron and other elements have significant covalent character. It's not as simple as saying, "Iron loses three electrons to make Fe3+." That only occurs when a compound like FeCl3 dissolves in water to make the ions.

Chemically, the most common oxidation states of iron are iron(II) and iron(III). However Iron forms compounds in a wide range of oxidation states, −2 to +7.

The stability depends on the compound, there is no rule I know of.

Francium isn't Iron. What the hell are you smoking?