The indicative form of the participial wrought is wreak. The indic. of part. fraught is freight, and sometimes one will see that made into a weak verb, thus: freighted (an ugly word, IMO).

I have, in fact, seen rive used, though my reading tends to be wider and more inclusive of the antique than many folks'.

The German for "preach" is predigen, so there's a common root there. German for "teach" is lehren, which I think is related to the English word "lore," OE lar. I think both predigen and lehren are weak verbs in German.