Halo 3 and Halo 3 ODST question?

[Reza B]

Alright, Sargent Johnson dies in Halo 3, but how come he's alive in halo 3 ODST????????
and what the hell happend to masterchief when he got left in space after firing halo?????
and why isn't he in Halo 3 ODST???
and who the hell is Dare???

 

[spsay]

Halo 3 ODST takes place during halo 2 while master chief was at delta halo, that is why sergeant johnson is still alive. The current status of master chief is still unknown and may be used to make a new Halo but as for now it is not clear what will happen to him.Dare is a new character to be shown as well in Halo 3 ODST like Romeo and Dutch