Assertions in exams

I’m a bit confused about the use of assertions in some past exam questions, and hope someone can clarify for me.

I thought assertions relating to Balance Sheet balances were:
Completeness
Rights & obs
Existence
Valuation & allocation.

…but in the June 08 exam, question 1. c) asked for the assertions relating to the receivables figure…
the ACCA answer is
Existence, Rights & obs, Valuation & allocation, and Cut-off!?

I know that cut-off could be said to be a part of ensuring completeness, but it’s not all of it.
The marking scheme makes a reference to completeness, but in relation to unrecorded invoices only (ie. not neccessarily cut-off).
So what do we do in the exam if we’re asked about assertions relating to balances?
I’m confused as to what ACCA want.

The second confusion I have around assertions in the exam is when the question asks us to give the “purpose” of a substantive test.
Do they want us to give the assertion we are testing (even if they make no reference to assertions in the question), or do they want us to give a more “test-specific” purpose.
eg.
Test:
for a sample of credit notes, agree to supporting docs & check all are authorised by mgt
Purpose:
to confirm that credit notes are only issued and sales entries reversed when there is a valid reason

or do they want

Purpose:
To confirm the accuracy of the sales figure and/or
the correct valuation of the recievables figure.

Different types of answers seem to be given to each question, but I can’t work out the logic/clue as to which answer they want from us.
I suppose it would be possible to write down both types of “purpose” in the exam…but with time being short it will take longer than it should to answer.

If anyone has any advice, or tips as to how to deal with these 2 types of assertion problems, I’d be very grateful.
Thanks.