https://www.canada.ca/en/immigration-refugees-citizenship/services/work-canada/permit/temporary/work-permit-types/fee-exemptions.html
You can find from the above link for fee exemptions of different types of visa status. Convention refugees are exempted from fee payment.
What happen during biometrics? Will they ask any questions? After biometrics, how long it takes to wait for the eligibility interview? Normally, people get their open work permit even before the eligibility interview?