He'll answer the simpler question first. "If a new god chooses the cleric, the cleric starts at their old level."
"...and." Esta is not sure how to put this simply, in the vocabulary they now have left. He told Merrin, a couple of days earlier, that this would be an easier conversation to have, if -- "The Outer Gods are not usually on nice -- happy, fun, good -- terms with the gods of Pharasma's Creation. Though --"
Esta speaks more slowly.
"The one that brought us here might be different."
Yog-Sothoth runs spacetime for Creation. It is the only Outer God that Pharasma actively worked with to establish Creation. That's one reason It is Chaotic Neutral, like the Maelstrom that predates Creation, rather than Chaotic Evil, like Rovagug that wants to eat Creation. It could count as Lawful, even, like Jerishall, or pure Neutral like Gozreh; except for the part where, instead of that, It classifies Chaotic.
...Esta is pretty sure he didn't know any of that one year earlier and he does not per se remember actually learning it at any point.