You need to have done AS FM1, in order to sit AS FM2 to as well.
The AS is very easy and not too difficult as long as you have practiced all the questions in the textbooks and for additional practice from other exam boards too.
Most of the content is the OLD M2, M3 and some M4. Those papers run from 2001 to 2021 with the IAL being exactly the same.
Good luck in practicing papers
AS-LevelFM1The following topics are in AS FM1:Momentum and impulse old M1 and M2.
Work, energy and power old M2.
Elastic collisions in one dimension old M2 and M3.
FM2The following topics are in AS FM2:Motion in a circle old M3.
Centres of mass of plane figures old M2 and M3
Further kinematics old M2 and M3
A-LevelFM1Momentum and Impulse is a topic in the old M1
Work, Energy and Power used to be in the old M2
Elastic strings and springs and elastic energy also used to be in M2 old
Elastic collisions in one dimension M2 old too
Elastic collisions in two dimensions M2 old too
FM2Motion in a circle only featured in the old M3
Centres of mass of plane figures only featured in the old
The rest of the topics build up from M2, M3 and some in M4 old.
Further centres of mass
Further kinematics
Further dynamics
Further kinematics