Edexcel A Level Maths Paper 2

My friend who has access needs sat a completely different Edexcel A Level Maths paper 2 than I did. Most likely than what majority of the country sat. What will this mean, since everyone is supposed to sit the same paper?

How did this happen?

There's always a petition.
The access arrangements paper for some qualifications do have small differences, perhaps if a more drastic decision has been made then it is a different paper. Without comment from the exam board we are taking the word of students who sat 1 paper and students who sat another.
What does this mean? Absolutely nothing.
You say "everyone is supposed to sit the same paper", but that isn't true by the very fact that there is a different exam paper for some students with access arrangements.
I'm not really sure what you are asking beyond "is this allowed" - where the answer is yes.

It’s not small differences they had 16 questions which was all different topics than what we had. Every single question was different