You can attend COA and CIIP even without a visa while PDOS requires a Visa I think.
Ive attended COA this month and will be attending CIIP next week and I dont have a Visa yet.
Ive cleared this with them when they replied to my schedule.
This is a privilege I think for those in the final stage of their application.
Btw, im also waiting for PPR so Im taking advantage of these seminars, its FREE anyway and very informative.