Yes, the convocation is the ceremony.

Graduation is a bit more complicated. Its definitely not when you have finished your last exam. However passing all required units will make you eligible for graduation. Depending on the university, it may not be automatic. If its not automatic, then you'll need to put in an application for graduation, where upon approval (they only need to verify that you've indeed completed all requirements to graduate, and mark you as no longer continuing being enrolled) then you'll be eligible for the convocation ceremony.

Before the convocation ceremony, you may not have the certificate for the diploma/degree that you're working for as yet. However you can request the admin of the school/department/faculty you're at to issue you a latter confirming that you have indeed fulfilled the requirement to graduate, and is awaiting the ceremony for the certificate to be given to you.

Job being found before graduation, this depends on the person too, but mostly it depends on the course itself. Certain courses which are in high demand such as mining engineering can have industry recruiters scouting the universities for 3rd year students for possible recruitment.