I thought the paper was fair and other then all the question 3's being labeled 2.x didn't find any horrible errors
I ran out of time though (I don't know about anyone else but I found myself constantly crossing my prolog programs out due to errors and having to rewrite them which wastes a lot of time - Oh how I wish for a world where i could do exams on computers...) and as such I can't answer your question regarding 6.2 as I only just finished 6.1 as time ran out (A pity cause means end planners are fairly easy marks).
Based on my answer for 6.1 and how I remember question 2 looking I don't think the answers should have been similar, If i am correct the non protected goal version should go into an infinite loop fairly quickly while a protected one should not and will have a lengthier answer