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

What are oxidising agents?

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

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.

TiCl_3 acts as a good reducing agent. Why ?

Give two oxidising agents?

Can PCI_5 act as an oxidising as well as a reducing agent? Justify.