R2 decision release dates are going to vary by school. Most are between late March and mid April. As for WL decisions those are much less concrete. Usually WL decisions are released on the decision day of the next round (i.e. if you were WL in R1, you'll have a status update on the R2 decision day). However, this once again depends on the school. Kellogg gives WL answers to some applicants in between rounds. Also remember that if you get WL you can remain on the list through subsequent rounds. There are R1 waitlisters who didn't find out a concrete decision until just last week. There's really no way to pinpoint when you will have a final yes or no if you are WL. Schools do realize that for international applicants there is a date beyond which it would be unfeasible to get a Visa. However, that doesn't guarantee you a sooner answer. Schools encourage international applicants to apply in R1 or R2 to leave plenty of time for Visa processing. You shouldn't have any issues getting your paperwork completed in time if you applied and were accepted in R2.
As for the order applications are read, this also depends on the school. If a school has rolling admissions then your application is read when it's submitted. CBS does this. However, schools with firm round deadlines don't start reading applications until after the deadline and they are reviewed in no particular order. If you look through the "calling all applicants" threads you will see that whenever interview decisions start coming out everyone wants to know "oh when did you submit our application?" thinking that will be an indication of when their own invite arrives. There is no correlation. Whether you submitted 10 days before the deadline or 10 minutes before, the application is reviewed whenever it gets reviewed and an invitation to invite comes if and when it comes.
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