The Great Schism of 1054 was a very big deal, particularly with regard to major disagreements in Church Doctrine and institutional power.
The main disagreement which led to a "Schism" between the Roman rite and Eastern rite Churches, was the concept of the Trinity. If my memory is correct, the Roman Catholic Church's position was (and is), that the ...
Sort of, but he was not recognized by all the electors, some of whom elected another candidate. I can find no evidence that he was ever confirmed as bishop by the Holy See. In short, it's complicated...
Canon James of Tonengo, previously chaplain to Pope Urban IV (d.1264), was one of two Bishops of Vercelli elected by different factions of electors:
Italian Wikipedia states
Martino Avogadro di Quaregna † ( 1244 - deceased July 1268 )
Vacant See (1268-1273)
Aimone di Challant † (21 December 1273 - 19 June 1303 died)
The arch-diocese itself lists as bishop:
Aimone di Challant (1268 – 19 giugno 1305)