Well i can Remember i had to enter UCI on the submission form as UCI is document ID for Permanent resident card itself which can be used as attachment.
http://www.cic.gc.ca/english/helpcentre/answer.asp?qnum=772&top=4
UCI does not represent here for Parents or Grandparents but for the applicant itself.
And the information in grey area you have provided is for new Applicants, Not for the Interest to Sponsor.
3. same E-Mail ( may be / form asked to enter twice to conform E-Mail)
Same person can use two different Email address.so on based of email the duplicates can't be eliminated.
Following criteria might be useful to eliminate duplicates.
(1) Match Applicants's Document ID in case of PR card it is UCI.
(2) DOB, Full name and Address of applicant.
(3) Full names and Dob of parents or Grandparents for this applicant.