On rereading it, I think the passive is possible for 14. I'm more
used to hearing "should not be treated in the same manner". I
rarely hear the verb "serve" in that context, so I was a bit thrown by
it!
"Please do not give it up unless it is essential" is possible.
So is "Please do not give it up because it is essential".
"I haven't got the original text yet, but if I do, I'll let you know." - Correct. "got" meaning "found".
"I haven't found the original text yet, but if I do, I'll let you know." - Better, in my opinion.
OR:
"I haven't got the original text yet, but
when I do, I'll let you know." - Also better. "haven't got" meaning "don't have". You can't say "
if I do" after you've said that you don't! That may be why you asked this question in the first place.
Also, 8 can be "was".
CJ