A Sorcery deck is an atlas of sites and a spellbook, led by an Avatar. Compare two lists to see the Avatar change first, then every site and spell that changed.
Deck A
Deck B

The Avatar is listed first, since it is the one card that leads the deck.
Sites and spells are compared together in one list, so a change of element usually shows as new sites next to the new spells they help cast.
Alpha and Beta printings of the same card are shown as a printing change rather than a new card, and the upgrade cost prices the exact printing.
The Fire precon from Alpha against the one from Beta: most cards return as a new printing, and a handful were swapped out.
Open this comparisonYes. An Avatar change is shown at the top, ahead of the sites and spells.
Yes. Both are in the precon list: pick one in each slot.
Yes. A printing change lists the printing in each deck, which matters when Alpha and Beta copies are priced very differently.
More in the deck compare FAQ.