Is it true that Partner Relationship Management is toll of Business Development?

I am not sure on this question but yes how you have relationship with your partners and customers it surely depends on business development as goodwill and reputation is also build by keeping partners and customers happy so it all depends on relationship in business to get more business for long term

Yes ,it is tru,but the effective communication and check and balance system is very important.

Yes.

Off course managing partnerships can be a separate designation on its own, depending on the company & its size & operations. I, as a business development manager, was responsible for building & maintaining bridges with partners & cross-functional partners to create new opportunities, sometime with them and other times through them.