Ideally you should mention different work experience for IBM and Collabera and if the case assessing officer asks, you can explain him, the idea is to correct your mistake as soon as possible once you realized it and always be truthful to case assessing officer. Also note that it should also match with your express entry federal application as well to avoid any issues later.
2. In the experience letter my designation mentioned as " Technical Subject Matter Expert". But I mentioned in PNP registartion as ETL Technical Subject Matter Expert because I worked in ETL project as a Technical Subject Matter Expert.