I'm not the developer but I might be able to help you out.

1)  The player character is always essentially the same person and is male.  The PC being male is required by the story.  Not only that the dialog, artwork, and story progression, are tied to a specific character and not modular (like other games where there is either a choice of starting characters which chance the story or the starting character can be modified at the start with those choices having effects on story or gameplay).  Each choice has strengths but this is the choice that Siren seams to have made and it really works out well for this game.

2)  There isn't combat in the traditional sense.  The most violence the PC does (so far) is shooting a sling shot at NPCs to stun them so they won't chase/stop chasing the character.  There are several more situations where the PC will need to use stealth to avoid being caught sneaking around.  Most of the difficulty in the game is in puzzle solving (both in terms of obvious puzzles such as how to push rocks around but also the more subtle puzzles of how to progress the story and unlock extras).

3)  It's not obvious at the start of the game but there is something weird going on in the town.  The game isn't finished but I find myself trying to figure out the mystery of what exactly happened/is happening.  Hopefully as the game is worked on, the ending will answer these questions but right now that is a mystery I enjoy pondering.  There are things to discover in the exploration of the setting, backstory, personal histories of the other characters, the town, and the like but there aren't any "who done it" type mysteries that I recall.

The game is quite erotic with a compelling setting and well written story.  Many NPCs have internal conflicts the PC helps "guide" them through which adds depth to all the characters.  The game has parallel paths but each path is pretty much set by Siren and the game (so far) ends up at the same place every time.  It is largely non-violent and the puzzles add a challenge to the game but I believe they aren't designed to be a real hindrance to playing out the story.  If you get stuck somewhere you can ask in the hint thread here and people tend to quickly offer help.

I hope I answered your questions and gave you a better idea if this game is right for you.  Is there anything else about the game you would like to know?