1) unless you are a school student I'm pretty sure legislation state that you must be hired for at least 3 hours a shift. I don't think you could work 1 hour. And maccas would get no benefit hiring someone for 1 hour a week (even if they legally could). It costs to employ someone eg training, super, tax stuff etc
2) part time is generally 2 or 3 days a week. If you work less than that (and you are hired as a casual staff member) then you would write on your resume that you were employed as casual staff member. Don't over exaggerate your resume too much- what if a potential employer asks for a reference or gives them a call? You would be caught out (if you worked only 4 hours per week or something and said you worked part time).