Can I add Ubuntu 12.10 repositories to 12.04 to have the latest software and updates? If, yes, how can i do this? I know that by adding PPAs I can have latest software, but really, I do not like to use PPAs. So is there any way to use 12.10 repositories in 12.04?
If you want you can add them in /etc/apt/sources.list file. But, be warned that, you may face dependency conflicts later. Also adding them is like running 12.10 without upgrading. But anytime you execute the upgrade command, the system will be upgraded to 12.10. So, there is no benefit adding them to 12.04 without using the upgrade instead.
If you wanted to have an upgraded version of some apps only (and wanted to remove the 12.10 repos after doing that), then I strongly advice you not to do that. Because upgrading to an updated version will/can put your system forward and after removing the 12.10 repos, you'll face numerous problems with dependency from the non-upgraded packages.
