inform of [maybe on too*, my mind's gone numb! let's hope someone else answers] and inform about are sometimes interchangeable, but not always:
I was not informed of the late running of the bus
= (I think)
I was not informed about the late running of the bus
Another possibility would be
I was not informed as to the late running of the bus
Use of when the object is specified, about when it's not.
Head Office must be informed of the burglary.
Head Office must be informed about any breach of security.
Yes. This is OK too:
Your job is to inform the committee on the state of the roads in the area. About would be OK too; of would imply a bad state: It was your job to inform the committee of the state of that road; there might have been an accident. This is not easy, as you will have noticed. Over to someone else...