The concept of creating a unique and complex experience for every player is interesting. How far is this taken? I enjoy experiencing everything a game has to offer when possible.

• Can you reasonably see everything (minus minor content) this game has to offer? I am not worried about small details such as unique dialogue, encounters, etc. Only what would be required for "completing" the game, whatever that definition is.
  
  
• The achievements seem rather untouched, and I have heard there are many community puzzles to solve. Are some difficult or not obtainable for the average player? Are you able to reasonably complete them all?

While these are not a deal breaker for me, I try to do research whenever possible to make certain I will enjoy the product. In this case, I could not easily find information except for outright walkthroughs. If possible, please do not include any spoilers unless they are relevant to the questions. Thanks!