Hybridization of fe in brown ring complex and why fe is in +1 oxidation state . I think fe is stable in only +2 and +3 .

The OS of Fe in Brown ring is +1. The complex shaped is [Fe.NO.5H2O]SO4..The charge on anion is - 2. Subsequently charge on cationic complex must be +2 as ring is electrically unbiased. The charge on Fe on computation turns out to be +2.. Be that as it may, electrontransfer happen from NO to Fe. Thus No and Fe secure a charge of +1 each. 

Consequently the OS of Fe in dark colored ring is +1, because of charge exchange amongst Fe and NO.