Mock exam questions very often do not crop up in the real exam. Your tutor sounds typical of the modern system, they follow the guidelines and can offer no argument because they are clueless and technically inept.
Question 1 sort of answers itself, absorbent in the question watertight in one of the answers.
Question 2 I would argue there are two answers. b) long vertical runs place undue stress on conductors. c) premature collapse in the event of a fire (see Section 521).
Question 3 you are correct.
No in the UK there are no legal restrictions on people carrying certain electrical works although some of it must be notified there is nothing stopping the home owner from doing this.
Installed some of this at Pinewood Studios in the late 80s have no idea where they obtained it from could have been specially made as they had their own ideas there.