How to interpret Law of conservation of strangeness? Is there a recent explanation of Law of conservation of strangeness? and why does it not work for reactions taking long times like $10^{-10}$ seconds?
 A: It isn't true that processes that change the strangeness can't be faster than $10^{-10}$ seconds. For example a top quark can decay into a strange quark, which changes the strangeness by $+1$, and that takes around $5 \times 10^{-25}$ seconds. However it is mostly true, and this is why.
Incidentally you might want to have a look at the Wikipedia article on strangeness, where the conservation of strangeness is discussed.
Strangeness is the net number of strange quarks i.e. the number of strange quarks minus the number of antistrange quarks. There are no processes involving the strong and electromagnetic forces that can change the net number of strange quarks, or indeed any other types of quark. They can only create or destroy strange-antistrange pairs, and this leaves the strangeness unchanged.
Weak interactions can change the net number of strange quarks, but they are usually (relatively) slow. So for example the strange quark decay to an up quark and $W^-$ boson via the weak force takes around $10^{-10}$ seconds. This is the reason for the time limit that you mention. Most processes that take less than $10^{-10}$ seconds involve only the strong and EM forces and therefore those processes can't change the strangeness.
A: 
How to interpret Law of conservation of strangeness?

There is no such law. See the Wikipedia article: "Noting that collisions seemed to always produce pairs of these particles, it was postulated that a new conserved quantity, dubbed 'strangeness', was preserved during their creation, but not conserved in their decay".

Is there a recent explanation of Law of conservation of strangeness? and why does it not work for reactions taking long times like $10^{−10}$ seconds?

I don't currently know of a satisfactory explanation for the preservation of strangeness during particle creation. Because I can't currently explain what strangeness is. Strangeness was introduced because some particles such as kaons took longer to decay than others. As for how this actually works, I can't say in a fashion that will satisfy you. The Wikipedia article says this: "The strange antiquark of the kaon transmutes into an up antiquark by the emission of a W+ boson; the W+ boson subsequently decays into a down antiquark and an up quark". But there's no explanation of how or why this happens, and no explanation of how it can happen when the W+ boson has a mass of 80GeV, which is far more than the kaon or the resultant pions. And there's no explanation as to why a billionth of a second later, all the strangeness is gone. Sorry.    
