PMI-ism's Quality?

Who determines quality metrics and keep finding ways to improve quality?

Who recommends improvements?

Should consider Quality if one of the project constraints changes?

Could there be a separate QA department performing some quality activities, i.e. quality audits?

Differences among: Plan, Perform and Control processes?

Pareto diagram purposes?

Cost of Quality, is it a tool for Control Quality?

Project completed. The client is very satisfied with the delivery and the features added by the team without the client asking. Is this a successful project?