Modify work experience POST ITA

I have total 17 years experience out of Canada working over 7 companies (same NOC) .

  • For 15 years covering 5 companies, I have all reference letter, relieving letter, offer letter , sal slip.
  • For initial two years – the two companies are closed and I am not having anything except relieving letters. No colleague is traceable.

My question -

  1. Pre-ITA, I have mentioned all those 7 companies (17 yrs exp) , Now post-ITA Can I move those initial two companies into personal history… As score would be unchanged.
  2. Is it allowed to change work experience section post ITA ?
  3. Also I belive personal history should be only for last 10 years, Do we need mention work experience which beyond 15 years in personal history section.
  4. OR… I need to provide self notarized affidavit… for self reference-letter for those two companies ?