i think its a good chance

Doubt it, DS, DS2 and DS3 didn't get any.
However there's a chance as BB did though.

I think the outfits will count as the achievements.

None of the other souls games receied extra achievements even for the DLCs. Why would a small update get them?

Only BB got some for the DLC, but that's probably bcs Sony insisted on adding them.

Maybe for completing a gauntlet or getting a skin? Otherwise, I doubt it.

i already 100%ed the game and i still go back

I would say the game is really not designed around well for co-op. The way the combat works would either trivialize or make fairly awkward most of the boss fights. This is an issue to some degree with certain Souls bosses (usually the human ones, like Maria in Bloodborne, who becomes a total joke with summons, or Friede in DS3 who is super hard by yourself but is hardly challenging with even a moderately competent human companion), but I think it's clear that Sekiro is even more fundamentally designed to work as a single player experience. Now, I will say that a PvP area could be kind of interesting, and I *hate* PvP in all the other From games. But if there were a multiplayer aspect of Sekiro that could work well, that might be it.

No

People have made multiplayer mods and it doesn't work too good.

The game is simply designed for singleplayer and multiplayer wouldn't work lore-wise.

I don't think that would be a good idea. There are already some online mods, and to say the least, it takes all the fun out of Sekiro. Go check them out, you'll see what I mean.

Facts

JAJAJA

Download "SekiroFPSUnlockerAndMore", includes 21:9 support, custom framerate caps/framerate unlocking (144hz Sekiro is ****ing nice), and more

Just go to NG+ instead of making a new save file

Fromsoft has confirmed it will be 11 GB on console and 15 on PC

it's never wrong to start a new character

if it is of any help, the combat art can be activated from the blocking stance (holding L1 on playstation) and then pressing attack button (R1). I had trouble by pressing both buttons at the same time because sometimes the combat art didn't activate and found out this way it always works.