MM6 is the best game of the saga. You are totally free to go everywhere. Despite other M&M there's no level cap ( others chapters have a maximum level). What I suggest is to play without any patch, yes there are user patches that can fix a lot of minor things and details that you can forget unless you are a perfection maniac. This game is really near perfection, even the aged graphics have its own fashion, and you cannot still find other games with so detailed inventory. The version of the game delivered here on GOG is 1.2 wich is already patched (the most annoying bugs are already fixed). You can freely try of course other patches (guides on the forum), saved games can be easily backuped and re-installing the game from scratch requires ~1 minute. The replayability of the game is nearly unlimited. My first game took more than 150 hours, and I bought it again here after years. Best RPG of all times. You can play in relax mode and finish the game within lvl 50-60 or you can try to be perfectionist and try to reach higher levels before characters start to aging (by the way, your entire party is immortal, even with 150+ years you can still play). My advice is to forget abouy any guide and to explore the game yourself. First play should be mandatory Relax mode (that's not a game type, just a different approach to the game! :P)
