Totes just ignored me ahahahah.
Ex1 : is 100 achievable ? AKA which year is it the closest in difficulty to
Yes your friend is able to come, as it is for 2U.
Of course 100 is achievable, by many I believe.
The question now is, can you handle dealing with harder questions as well as a fairly pressuring time limit, or are you only able to deal with harder questions? I cannot say which paper it is closest in difficulty to, but I can say that I feel that the average difficulty of the 2015 paper is higher than other years, but the end of the paper is much easier than other years.
Question for 4U: how many 'famous' mathematical theorems/proofs are proved in the exam? e.g. last year there was Gaussian integral, the year before (iirc) there was a proof for 1/1^2 + 1/2^2 + 1/3^2 +..... = (pi^2)/6
Hard to answer because I do not know what the line between 'famous' and non-famous is. What may be famous to me may be completely unheard of to you.
But a well-seasoned student of mathematics will look at the paper and be able to recognise 6-7 results and know exactly what the question is doing.
Hey Carrotsticks, is it too late to sign up?
For Extension 1 and 2, yes.
For 2 Unit, no.