There is actually no "aquatic" terrain, it's "water" terrain.

The biggest problem my DM is insisting on is that "cold" terrain as just being cold sounds out of place, because it's not really a terrain type and is more about climate type (on the scale of cold/temperate/hot) and is out of place among other choices, so it's got to be the terrain type - like glaciers, tundra and such. But those almost universally can be described as cold plains (or maybe deserts). Or is the same as with jungle not being treated as a forest?

Case by case defining of every creature type sometimes slows things down, but, I guess, it's inevitable.

Also, on the latter, how the things change if I dip into ranger and actually get favored enemy?

I am obviously trying to get some Paizo™-approved answers, because the first three questions are up to debate. I am not sure if I'll be able to get those, but it doesn't hurt to try.

The example in Deadly weapon quality states that master quality weapon deals two listed dice on critical hit, but the example states that master quality rapier does additional 2d6 damage, not 2d8. I suppose that's a mistake.

Also, offtopic question. I didn't find anything about crit confirmation. Does this mean that any attack that is nat 20 or exceeds AC by 10 or more is already a crit?

You are forgetting another thing: tactics. From rogue viewpoint: flanking is the most often way to sneak attack, and with cleave, sneak attacking both targets is ridiculously hard(not of you're orc rogue, though, but this is only one case).

Overal, cleave is similar to vital strike. You get more damage than from usual attack as standard action, but you get less damage compared to fullround unless you build focus is cleaving, in which case they are awesome and cool(According to my experience, killing 3 orcs with single cleave at lvl 5 is ridiculous). The only really huge positive side of cleave is free move action, which makes you quite mobile in combat.

Consider darkleaf outfit. It will cost you exactly 2 pp and save more weight than mithral rapier and darkwokd buckler. Still, you may just not dump str that hard. You can get 13 int and 8 str, and then put a point in int at lvl 4. This will make your life much easier. You can instead go with 17 dex, which gives you even more spare points, but that's a hard choice(I went for it, though, and regret nothing. Totally worth it).

You've created two topics. I have said everything I wanted in another one, but want to add: if you won't dump str so hard, you may not need dex to damage that badly. This will allow you to get combat reflexes at lvl 1 and increase your survivability and make you extremely hard to kill. My first swashbuckler game was as pregen, which had no dex to dmg at level 4 and still was surprisingly good. Don't try to get most damage possible at first level, barbarian with greatsword will wipe out more enemies and you have to deal with it.

Mithral rapier is really not worth it. If you need to pierce silver DR, chose silversheen. It doesn't rust, which may help at some occasion. Masterwork buckler is enough, the only reason to buy darkwood version is 0% chance of arcane casting failure. Lowering outfit and armor weight is more efficient.

About build - SERIOUSLY consider extra panache feat. While having bigger panache pool as inspired blade, you can't restore it via killing blows, so, in case you're unlucky, you will get two more parry and riposte uses. I'd say that inspired blade is a bit overrated because of the reason above and I chose more reliable option(only noble fencer archetype), but considering your 6 str... yeah, you really need that dex to damage.

And 6 str can kill you. Literally. There are ghosts which do 1d6 str damage, and I met them in PFS at least twice. Maybe even three. Not the case. Besides the encumberance reason mentioned above, stat damage can come unexpected and with terrible consequences.

Kyonin fans, hmm? weird...

False rumors. Those pathfinders are stuffed shirts! Ezren's okay though. I GUESS.

That's it. Some elves are literally trying to copy your style. I can bet I saw couple ot them working with Society.

Oh, and the question answering isn't free. Just because you don't realize what I take in payment doesn't mean I don't get paid.

Well, what kind of profit do you get then?

Reflexively checks his jewelry and pockets. Just to be sure.

I literally can't believe Merisiel is just answering any questions this freely. Truly, a fortune!

Hello, Merisiel. That's a shame you've never visited Kyonin, your skill with rapier is greatly known and respected in there. And even made you some fans, cough cough.

Catfolk friend if mine wanted to ask you, what is your opinion on their kin.

Rumors tell, you help Pathfinder Society sometimes. Even if they are false, which faction do you like most?

Are you more sneaky than flashy or more flashy than sneaky rogue?

Actually, first feat description tells: While using this style, you can make melee attacks with the chosen weapon as if it were a heavy mace. So, perhaps, if you have weapon training with hammers, this will work?

Do ranged weapon count as melee with empty quiver style(or with advanced feats in this style)? Especially, in terms of feat like this:
http://www.d20pfsrd.com/feats/weapon-mastery-feats/difficult-swings-weapon- mastery/
So, the question is, does this feat work if I make
with this style:
1)Ranged fullround?
2)Melee fullround?
3)Combined melee/ranged fullround?

If no, can you, let's say, quickdraw melee weapon with WT during fullround and make last attack with melee weapon, so you will make adjacent squares difficult terrain?

Let me disagree with elf rating. Adventurer's guide introduced us a realy damn neat weapon - elven thornblade, which is 1d6 18-20 weapon that has +2 to crit conformation(Which is vital for panache regain) and does both S and P damage type, so it lets you use finesse without archetypes and untill you get slashing grace. Using this weapon is worth feat(because +2 to crit confirm is half of critical focus and additional damage type is half of weapon versatility that doesn't require your swift action)

Also, I'd like to point out martial mastery feat, which opens up even more options(It's sad that swashbuckler training doesn't count as fighter weapon training, but this would be too OP because it includes weapons from couple of weapon groups). Difficult swings is nice to have, but one option I'm going to use as my PFS swash is taking 13 str to qualify for Cut from the air feat, which lets us parry BOTH melee and ranged attacks. This may be not as useful as awesome, but being awesome is one of main reasons to play swashbuckler.

By the way, why do you consider TWF useless? Of course, we will require another feat to apply dex to dmg with slashing grace, but the only feature you actually lose is precise strike and only during fullrounds, in which you still get more damage and can critfish for more panache. This is cheesy and requires bunch of feats, but is still worth it.