Yo!

So I've heard all about the new 2.5/2.6 hacking news and was wondering..

If I bought the new GTALCS it wouldnt work, but how can I see if it is the old one?

If I buy it used ad EB Games for example, the clerk told me that I could try it out, but how am I gonna see if it is the right one?

Is there anything I could put on my original memorystick to see if it is the right one?