`SO_2` act as both oxidising and reducing agent but `H_2S` acts as only reducing agent. Why ?

SO_2 acts as oxidising and reducing agent.

TiCl_3 acts as a good reducing agent. Why ?

How H_2O_2 acts as a bleaching agent ?

Pb^(4+) acts as an oxidising agent but Sn^(2+) acts as reducing agent, why ?

H_2O_2 is acting as a reducing agent as well as oxidising agent

Explain that SO_2 can act as an oxidising agent as well as a reducing agent, but SO_3 can act as an oxidising agent only.

Which is poorest reducing agent?