You will only need SAMRA and SARON for ATPL since you have to have the Multi-IR. INRAT is for the instrument rating. You have to have the instrument ride done in multi within a year as well. and co-pilot time counts half towards the total time only. and to write SAMRA and SARON, you will have to have 750hours total.
If this is a conversion other than from the states, you will have to have all the requirement including foreign ATPL before the conversion, otherwise you will have to do commercial ground school, written exam, commercial flight test, INRAT, IFR flight test in multi. If it has been more than a year from the initial multi ride or you don't have 50 hours multi PIC, you will have to do the multi ride as well.
IF you have foreign ATPL and have all the requirement, you will need to write PSTAR, SAMRA, SARON, INRAT and IFR flight test in multi.
There is no frozen ATPL in Canada.
I hope this helps.