No level requirement you just have to visit Windhelm four times at night (i think) and it should happen on the last visit.
Serana or Lydia i'd say, although Dragonborn (i think) stops Lydia saying her catchphrase occasionally it adds in some new lines. like "I don't know whether to kill it or pet it."
If your not getting dragon souls check any mods you have (if you do) that affect dragons and makes sure they were updated for the Dragonborn dlc (it made changes to how the souls work), also check your load order. You could try the command -
setstage mq104 90
But keep a save from before trying it if you do and afterwards go see if other dragons are working properly (they should then be at their lairs).
One file will always be missing when you validate the game, it's likely the file that automatically detects what hardware you have (it has always popped up after i've validated and launched the game with Steam).
If you check his bugs list it can happen, he's involved in a random encounter and i think the game can respawn him for it (and some other Companions if they die).
Leveled items don't get better with you, but getting them at later levels will get you a stronger version (and then it'll be set at that level). Skyforged weapons don't though.
If you check the forges bugs list, it suggests removing and replacing the sigil stone to try and fix the bug. I don't think that always works though. If you really want to get something different you might need to make the unenchanted weapon and enchant it yourself. If your on the PC the unofficial patch fixes it.
Oblivion is a bit more of a traditional rpg than Skyrim, you have to pick a class and theres more stats.
Some PC's aren't really up-gradable, if yours doesn't have a tower you probably can't.
Try and get back to the temple precisely a day after arranging it, if nothing happens then try waiting a hour (although that could also make the marriage quest fail). If any of your mods affect marriage make sure their correctly installed, and check through their comments (and bug reports if they have any) to see if it's mentioned there.
Spend sometime fiddling with the character creator, on PC there are mods and pre-made characters (those usually depend on the mods though).
Sneak attacks shouldn't affect magic damage like they do with physical attacks (without a mod for it installed on PC).
This is quite an old thread, the bug does have a section on the shouts bugs list here.
And all the loctaion id's are on the page here (teleporting to some may mess up quests though).
Same thing happened to me a little while ago. If i remember right i took her to Riften (so away from Darklight and the quest triggers) then tried recycleactor but she kept doing it until i went through all the repeated dialog a few times. That quest can apparently reset instead of completing properly so you could also try the command -
setstage dunDarklightQST 60
If your 360 is connected to the internet you can buy them from it's online store, if not you would have to get the physical Legendary Edition (Skyrim with all the dlc included on a disc).
There are some spots in walls and floors with very small gaps in, with a bit of force (like Whirlwind Sprint) you can pass through them and out of the game world.
The wiki has very long timeline page listing all (or at least most) known events and their dates.
Girls can bring home one of two foxes or a rabbit, boys a mudcrabs or skeever.
Deathbrand is from the quest Deathbrand (which you can get from the book Deathbrand if your level 36 or over). Black Guard from a quest for Glover Mallory if your in the thieves guild. All this is on the wiki.