Answer
The Marines started out as 20 space marine legions[1]. After the Horus Heresy the Emperor was afraid of it happening again so he made chapters which have 1000 Space Marines each thus no-one can have a massive army and rebel, as Horus did. Now after the heresy, the loyal Space Marine legions were made into smaller chapters, it is said there are about a thousand[2]. From that 1000, 234 are named - discounting destroyed or missing chapters. This leaves around 764 unnamed Chapters.
1) http://wh40k.lexicanum.com/wiki/Space_Marine_Legion 2) http://wh40k.lexicanum.com/wiki/List_of_Space_Marine_Chapters
Yes.
There are a total of 12 chapters in Dead Space.
15 chapters
AnswerUnlike the space marines, the chaos use not chapters but legions. The most popular legions tend to be the black legion, the iron warriors, the emperor's children, the red corsairs, thousand sons and many others. The codex of the smurfs or chaos will tell you in more detail
It depends what you want. There are many painting guides for many chapters. If you are a novice your best bet would be to ask someone at your local GW for some help.
10
A space marine scout bike squad is 70 points
Space Marine Tactical Squad (includes 10 Space Marines) Space Marine Combat Squad (includes 5 Space marines) Space Marine Rhino Space Marine Scout Squad (includes 5 Space Marine Scouts) Space Marine Assault Squad (includes 5 Space Marines).
A space marine captain costs 100 pts, but there is nearly half a page of upgrades to give him.
Read the codex
Games Workshop deliberately left them out so people could make up a history and color scheme for themselves. Same went for the missing Space Marine Primarch. It is just so people can have a little freedom when doing background stuff for their armies.
AnswerYou can create your own chapter as long as it is not copying another official or unofficial chapters. Therefore you can use your chapter when playing the game