1) It's usually 15 marks for content aka 15 points for content
in summary.
Advice is to use your COMPREHENSION skills.
It's the only way, considering it's a comprehension paper.
2) Common sense says, avoid useless information.
How do you tell if it is useless information?
Read the summary question thrice, underline what it is asking for,
and use your COMPREHENSION skills (lol).
No joke. Also make sure it is grammatically sound, or else marks
will be deducted and you'll end up with just 15/25 even with all 15
points.
Other than that, I probably don't understand your question.
3) Yes, you still should not be lifting entirely from the
passage even though the answer can be obtained solely from the
passage.
Marks can be deducted even if it does not say "use your own words"
at the discretion of the marker.
4) Don't know. I replaced the word "children" with "miniature
homosapiens" once.
I didn't get marked wrong, but my teacher advised me against doing
that in the examinations ever again.
Just remember to write short and sweet sentences that are
concise and to the point, and you won't go wrong for any section of
the paper.
I've gotten 23/25 for summary multiple times simply by
getting all 15 points right (through reading, understanding and
answering the summary question) and occasionally replacing a few
words here and there. Some words almost can't be replaced within
the stipulated exam time, don't panic.
For "own words" question types, feel free to replace
word-for-word, or just rephrasing with different usage of
vocabulary, just make sure it's still easily understood and the
meaning of the sentence has not been altered.
Good luck for tomorrow.
Hope you read this on time. I'm going back to Amaths revision for
Thursday's paper. Ciao!