Shalom Aleichem Rabanei hakolel, Shlit"a.

From the sugya regarding the perisha of the KG, it sounds as though Rabbi Yochanan & Reish Lakish agree that there is a dioraisa obligation to do so before Yom Kippur (though they differ on the biblical source).

In a separate disagreement on 3b, Rabbi Yochanan says that only in the case of Yom Kippur is there a biblically mandated perisha, whereas for the para aduma it is a "ma'ala bi'alma" (presumably meaning it is dirabanan), in contradistinction to R' Yehoshua ben Levi who holds that even in the case of para, the obligation is biblical in nature.

My question is as follows. Tosfos (4a, s.v. "Nichnisu") assert that the whole limud from miluim which R' Yochanan makes to learn that the KG must be sequestered before YK is an 'asmachta bi'alma". In other words, it too is dirabanan! But if that is the case, what is the difference to R' Yochanan between YK and para aduma? One is just an "asmachta bi'alma", and the other is just a "ma'ala bi'alma" (i.e. they are both midirabanan)!

From R' Yochanan's remarks on 3b in his machloikes with R' Yehoshua Ben Levi, it sounds as though there is a requirement me'ikar hadin to have perisha before YK, whereas para aduma is just an auxiliary case, but I fail to see the difference if they both truly. dirabanan.

Thank you very much,

Shalom Spira, Montreal, Canada