Kinda hard here to answer from an American English view.
If the spelling/usage of principle is correct, then "of" might be better. If principles, then perhaps "that" would work. If Principal, then "such as by" or "by". Without some previous context, this one is difficult to fully judge and hard to make sense of.
I'd expect a comma after condition to make it a clear before and after comparison, but it still reads strangely to me. I'd almost want a "thus" instead and again it would need some context to work smoothly as-is.
This one is good and correct, though "that" works just as well.
Both "that" or "as" could be used here and would mean the same thing.
Ok, after a bit more research (and I apologize as the internet is very bad at giving any information on this particular construct), it is not ungrammatical to separate "such" and "as" in a construct like this:
such (noun) as (verb)
Where in the first sentence's:
boys will be rewarded by the principal
is treated as a noun and
is the verb. It reads very tersely, but with your noun changed to principal, it is understandable.
The second is the same construct, though I believe there is a lot of implied information here that is being omitted:
was the condition (of the noun/object/subject implied)
was the treatment (to the previously implied noun/object/subject)
Here, because of the construct, we assume the second is a verb even though we have to work a bit to make it so.
A poor source...
If someone else has a better source or more info, please post as I admit the above information is a bit sub-par without a good source for further research.
In real life, the only time I come across this sort of construction is within the King James Bible and other older texts, so it is very edge case.