Well we use the heinemann textbook which is so crap so its a definite disadvantage over those who use grivas.
Anyway I asked my teacher and she said there's two main types of control questions: 1) Probable lie questions (intended to slightly increase arousal) and neutral questions which are questions like "what is your name?" etc. 2) Then there are positive and negative which I already explained...
So in the exam you could talk about probable lie and neutral questions in regards to types of control or the other option is positive and negative.
Also to answer your other question... When replying with a "yes" to a control question the arousal level may differ from when the person has to reply with a "no" for a control question. Therefore when asking relevant questions they can compare the negative responses with the negatives responses of the control questions. Because if all your answers were intended to be "yes" to indicate telling the truth the person may zone out of the questions and just sound like a machine on repeat i.e. yes...yes.. yes...yes... So that's another use of varying these control questions allows you to vary the relevant questions.
E.g. Back to the Sally example: Were you born in 1999 she would reply "no"......Did you steal the packet of salt and vinegar chips from the Milk Bar? she would also reply "no".... This would be most appropriate as the response in the control matched the response to the relevant question. Hence when comparing a "yes" in control to a "no" in relevant, the level of arousal may alter due to the varied response and not their feelings of guilt or anxiety. All in all it reduces the possibility of extraneous variables such as the required response (yes or no) from the participant from becoming confounding.
Sorry if you still don't get it from my explanation. But I hope you do

Let me know though.