Install mountain lion by using the .dmg from installer app

Question

I already have a Mountain Lion Installer app, downloaded from Apple Store.

Now, I would like to install ML on another machine I own. I didn't want to download it again, so I copied the .app to the other machine and try to run.

Unfortunately due to some error about mac unable to run the .app I wasn't able to install.

Most tutorial suggest to make a bootable USB starting by the installer InstallESD.dmg, found in installer .app. I would like instead to run the .dmg directly.

So I have three 'propedeutic' questions:

1. can I just mount and run the .dmg without making a bootable drive ?
2. I do have backup, a TimeCapsule one to be precise. In case of failure, can I just use the previous backup, and restore to Lion 10.7 ?
3. from 'Apple Store point of view', would my machine be recognized as upgraded and elegible for future update ?

Solution

1. No, you need to make it a bootable drive. Here's an exhaustive article on the process: http://www.macworld.com/article/1167857/how_to_make_a_bootable_mountain_lion_install_drive.html
2. Yeah, if you boot up using your recovery CD you can restore your entire system to a previous backup. http://support.apple.com/kb/HT1427
3. Yes, you will receive software updates for 10.8. Apple will likely charge for 10.9.