I'm pretty certain I recall seeing Brad comment that save games weren't completely compatible across betas. Personally, I would never assume compatibility in that situation with any game, but perhaps I'm just a bit pessimistic on that score.
Indeed. Very few games stop you from loading incompatible save-games, you just have to assume save games become incompatible after patching, unless otherwise stated.
...if I can re-found a city after one is razed, I should be able to found one after a foe surrenders. The land doesn't change between the 2 kinds of removal/destruction, so there should be a yield after a surrender, too.
I agree. One way or the other, yield or no yield, both actions should have the same effect. When a foe gives up, it even tells you they will scorch the land, but razing a city is the exact same thing, it's why you do it.