I'm trying to download or to get .dmg of iOS 8.4 or later and all I can get from Apple dev center is ipws file. Is there any way to convert/extract/whatever this .ipws to a valid dmg image (that can be eventually mounted ?) or is there any link from where I can get a valid .dmg image of ios8.4 or later? Thank you in advance
You'll have to decrypt it first, here is a complete guide to mounting and editing ipsw files.
Hope this helps,