By the power of truth, I, while living, have conquered the universe.
Posted by: bulldog534
*The last level, Halo, was that a remake of installation 04 and was that installation being created?
Yes, the Ark is what created the Halos. After Installation 04 was destroyed in halo CE, the Ark started to create a replacement.
*Why did the flood help Master Chief for like a quarter of a mission?
Because they needed to stop the Halos from firing, you form a temporary truce because (as the Gravemind says in Halo 2) "this Ring shall make us brothers". It's the one point that they share the same goal, and because Truth had made Johnson start up the firing sequence they had to move quickly. Halos fire, all life in the galaxy dies, meaning the Flood starve, so the Gravemind manipulated John and Thel to help him.
*The ark can create other installations?
Refer to my first point.
*Humans are related to Forerunners?
Somewhat.
Ten million years ago, the Precursors created humanity and the Forerunners - at this time, they were the exact same race, but were eventually split. The Librarian reveals in Halo 3's Terminals that she believes humanity to be special, which is expanded in Halo 4 where it's revealed that she has been indirectly nurturing humanity to fulfil a specific purpose in the future. She wants humanity to attain the Mantle (guardianship over life in the galaxy), and in so doing this allows humanity to use Forerunner technology.
Also, the word 'Forerunner' is just a title, it's not actually the name of the race we know as Forerunners. They saw themselves as just another stage in the universe and they would eventually pass the Mantle down to another race, thus humanity are the new Forerunners.
*Why did they fire the last halo, did that get rid of the flood somehow?
"The Ark is out of range of all the active Installations." ~ 343 Guilty Spark
The Gravemind dedicated all his forces to taking the Ark and the Halo, by firing it, Cortana's solution, they could wipe out the Flood without having to activate the other Halos.