A few demon's souls questions

[Lafiel]

1.)
you don't lose "everything" - you lose the unspent souls you are carrying (and if you die before reaching the point where you died before they are gone) and you lose some progress in the dungeon you are playing, but there are entry points to each dungeon after every boss demon, so that's very little actual loss ..

2.)
There is "online-coop" or rather the option to summon helpers. This isn't ment as a "co-op mode" you play with your friends (and it's not easy to play it with your friends), but to be able advance further than you would if the game was strictly single player.

3.)
"co-op"/online and single player are the same - the single player mode is online (if your ps3 is online)

you summon other players into your game or let others summon you to theirs (or break into other peoples games to take their bodies)

4.)
there is little actual story told.. you can hear some bits and pieces by freeing NPCs and talking to them but all of that is purely optional

for the first playthrough most people need 40-60 hours, although you can complete it in under two hours if you know what you are doing - I clocked 140h to do everthing, but I'll go back to try different approaches on playing the game ater I finished some other games

5.)
afaik there are about 70 different weapons, most of which are upgradeable with 15 different type of stones or special souls, and 34 spells divided into magic and miracles