acquisition valuation

You are correct in that the examiner has been inconsistent in doing it differently in the two questions.
There is however no ‘correct’ way – there rarely is a ‘correct’ answer in P4 because do much depends on assumptions and on estimates (the examiners answer is only a suggested answer – fortunately the P4 markers know what they are doing and alternatives are always accepted provided your assumptions etc. are sensible).

The real problem when wondering whether S’s shareholders will find an offer attractive is how much information they have. Most likely they will not be in a position to estimate synergy benefits etc. and probably will base their decision on the current share price of P.
However, obviously the share price of P is likely to change and so the actual benefit of the takeover to S’s shareholders will be based on the new share price of S.

There is therefore a logic for both approaches.

Again, unless obviously the question is specific, both approaches would be acceptable (provided you stated your assumptions and logic).

Theoretically, it should be the second approach, but not necessarily in practice.

Sorry that I cannot be more specific, but it is just not possible to be.