For the other question (Question 4), for part ii,the first magnet he gets can be any of the 5 available so thats 5/5 or 1, but when he opens the next packet, the probability he got the first one will be 1/5; hence the answer is 1 x 1/5.
Part ii, is kinda similar however the first try, it doesn't matter what he gets first hence it's 5/5, but on the second packet he can have any of the 4 remaining magnets he hasn't yet gotten so it's 4/5, and then the 3rd packet - he has two different ones already but he still has 3 to find so it's 3/5 and so on until the 5th packet where it would be the last remaining magnet hence that probability would be 1/5.
hence the answer would be 5/5 x 4/5 x 3/5 x 2/5 x 1/5
For Part iii, well, you just do 1 minus the answer you got from part ii. This is because part ii basically is the probability that he gets all types of fridge magnets in 5 packets, hence if he would be need more than 5 packets to get a complete set, it would be 1 - P(5 Packets).