All solutions here are SUGGESTED. Mr. Teng will hold no liability for any errors. Comments are entirely personal opinions.
Two direction vectors on the plane are and
Normal vector of plane,
Since both lines intersect,
Since is parallel to plane p.
Since lies on plane p.
Thus, lies in p.
Required acute angle
This question was well attempted. For (iii), some students might find it easier to plug the entire equation of into the equation of plane p and show. Aside from being careless in the vector manipulations, there were not much mistakes.