You
MUST sign your passport for it to be valid. Parents should
NEVER sign their child's passport -- this will make the child's passport invalid and you will need to apply for a new one.
Writing your address or Emergency contact is not mandatory but it is highly recommended you do. If you don't have a permanent address - write your current address. If it changes, cross it out and write the new address. Never use correction fluid on your passport - it will make your passport invalid. If you run out of space on your address page, write it on a blank piece of paper and use a paper clip to affix it to your passport. Do not glue or staple the piece of paper to your passport
Passport Canada Signature Policy:
https://www.canada.ca/content/dam/ircc/migration/ircc/english/passport/documents/pdf/signature-policy.pdf
Answers to most questions can be found on Passport Canada's Twitter account