Yes you can only pick one NOC as the primary one and this is the one used for the FSW points calculation.
Your work experience must be:
- In the same type of job as your primary NOC
- Within the last 10 years
- Paid work (volunteer work, unpaid internships don’t count)
- At skill type 0, or skill levels A or B of the 2016 National Occupational Classification (NOC)
- At least 1 year (1,560 hours total / 30 hours per week), continuous:
- Full-time at 1 job: 30 hours/week for 12 months = 1 year full time (1,560 hours)
- Wqual amount in part-time: 15 hours/week for 24 months = 1 year full time (1,560 hours)
- Full-time at more than 1 job: 30 hours/week for 12 months at more than 1 job = 1 year full time (1,560 hours)
No using the manager level NOC does not give you any extra benefits what does help is having CLB 9 is all four language abilities. This gives you double the points for the 3 years of work experience that you get points for.
Yes all documents are only needed at the ITA stage for the application stage you only need your IELTS and ECA’s. You can get extra points for having a brother or sister in Canada who is already a PR.