All solutions here are SUGGESTED. Mr. Teng will hold no liability for any errors. Comments are entirely personal opinions.
(i)
In order to use stratified sampling, we need to know the sampling frame. Since we do not have access to this information, it will be difficult to use a stratified sample.
(ii)
We line all the spectators as they arrive at the competition. Pick a random number from 1 to 100. For example, we pick the number 10 and sampling every 100th spectator starting from the 10th spectator in the queue.