AssetBundleManifest.GetAssetBundleHash chnanging hash

Unity Engine
1

When building bundles in 5.x they are build automaticly based on setting in assets/directories in project with dependancy (no Push/Pop api needed anymore). It also build another file(with folder name) which contains AssetBundleManifest object. Also Unity outputs *.manifest files. I assume thats only for me to check what is in every bundle and how look dependencies etc.)
So I download every time manifest file and load :

var abDir = “http:///domain/ab_out/”;
var manifestName = “ab_out”;
var wwwManifest = new WWW(abDir + manifestName);
yield return wwwManifest;
AssetBundle manifestBundle = wwwManifest.assetBundle;
AssetBundleManifest manifest = manifestBundle.LoadAsset(“AssetBundleManifest”) as AssetBundleManifest;

Then I check hashes of all asset bundles 5 times
for (int i = 0; i < 5; i++)
foreach(var bundle in manifest.GetAllAssetBundles())
Debug.Log(bundle+manifest.GetAssetBundleHash(bundle));

And I have 5 different hash sets of the same asset.

When I am using manifest from BuildPipeline:
var manifest=BuildPipeline.BuildAssetBundles ()

then every time I get the same hashes.

Why from downloded manifest I get different hashes every time?

2

And another question:
In last project in unity 4.x I’'ve used this strategy:
BuildPipeline.PushAssetDependencies();
//build Player
//build Assets
BuildPipeline.PopAssetDependencies();

In result in asset bundles there is no asset which was already in player. How can I do this in 5.x in which these methods are obsolete?