the guidance on the CIC site contradicts itself depending what link you use one link says any country 6 months or more and the other as you have quoted as per this link
http://www.cic.gc.ca/english/information/applications/guides/5525ETOC.asp#expect which interestingly has a link to the contradicting text.
As for definition adult life although i have no specific knowledge if were me applying now and had lived in more than one country i would just calculate a percentage and use that as the one for a certificate as the most lived in country and if CIC want additional ones they will ask. I would think if a 50/50 they may ask but if 75/25 probably not but who knows given the lack of clarity on the website. Ultimately is all about being up front with any info and if they want more they will ask for it.
