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That pre arrival what actually is it and does it mean success?

It outlines what services you can use in Canada - free - to help with process. Seems to basically be eligibility of PA so sort of just before final sign off ie DM.

Much variability in the sense that not all get or see in this exact order. But typically.
 
That pre arrival what actually is it and does it mean success?

It's a good sign.

IRCC will send you an official letter talking about free pre-arrival
services available before you arrive in Canada.

Once you receive this letter the PPR request will usually follow within a few weeks.