Water and hydrogen peroxide

Permanent hardness in water cannot be cured by :

The pair(s) of reagents that yield paramagnetic species is/are

Hydrogen peroxide in its reaction with $\ce{KIO4}$ and $\ce{NH2OH}$ respectively, is acting as a

Hydrogen peroxide acts both as an oxidising and as a reducing agent depending upon the nature of the reacting species. In which of the following cases $\ce{H2O2}$ acts as a reducing agent in acid medium ?

The reagent(s) used for softening the temporary hardness of water is(are)