Any build with a extra number at the end, 0.8.3.x so a 1 or 2 or 3 etc in place of the x is just a bug release. meaning nothing new just bug fixes for 0.8.3 build. So it has the same features as 0.8.3, just with hopefully most or all the bugs fixed
changing social group is just doing what a group likes. Nerd study, do well in school, pay attention in class etc, jock do well in PE class, stand up for yourself when messed with etc, cool kids, wear the best uniform you can that is not slutty, be aloof in school, mess with the nerds verbally etc, gopniks wear somewhat slutty uniform, skip class, don't pay attention when you go to class etc. After you do that enough they will invite you to join, how long it takes depends on your current rep with that group but as a rule of thumb it takes 2-3 months.
With that said you have to first lower your slut rep down, if you are a outcast slut. It does slowly lower over time if you don't do things to raise it. Also go to church, confess, attend mass etc all lower slut rep. Once it is low enough and you have done the above you will get a invite.
several things can effect willpower, drugs, alcohol, traits to name a few.