The Sacraments can be received from priests or bishops of SCHISMATIC groups WHICH HAVE VALID APOSTOLIC SUCCESSION, but only in cases of extreme emergency and upon imminent death. There is NO other valid reason for receiving anything at all from schismatics and no other circuмstance which would warrant even considering the possibility of same.
Oddly, if you Believe Pope Benedict XVI (ordained priest June 29th 1951) is a Schismatic, well, you could even receive communion from him in such a case then?
He has valid orders.
So much for Fr. Cekada's Una cuм theory....well?
Clearly, Benedict 16 was validly ordained a priest. I've never heard any sedevacantist dispute this. Therefore, in danger of death, he could validly give absolution
provided he has the intention to absolve sins.
In regards to Holy Communion, however, he has already denied the Real Presence in one of his books (I don't remember which one, but it has been quoted on this forum within the last few weeks), so I don't see how he could have the intention of doing as the Church does regardless of what rite he used.