What is strangeness
Strangeness quantum number S is a property of a particle and is used to describe/ predict decay.
Under which force is strangeness conserved
Strong and Electromagnetic
How does strangeness behaviour in a weak interaction
it can change but only by 0,-1 or +1
How is strangeness assigned
particles with a S quark have strangeness -1 and particles with a (anti)S quark have strangeness +1