If I understand what you are asking...I think you just need to edit the date format section of the global.php file in your language folder. See this post for details.
Making this an option in the admin section would be a big timesaver. Just a thought for the future....
I think what you want to do can be done using the Blocks admin section. In the center you have left, right and center blocks that all go in the "center" block. By setting those and the order, I think you can get what you want.
What module are you thinking about? Some modules can be installed more than one time with different names allowing you to give permission to some groups on one and other groups on another.
I don't think it is such a problem for users to have the same password. If it told you that, then all you would have to do to hack a XOOPS site or wordpress site is try that password with all the users. It is the user name that can't be duplicated.
Hello! You need to take a quick trip over to The Smart Factory as Marcan has done an excelent job already of combining all those hacks into one place for everyone. If you apply his hack your site will be multilingual and you will be able to switch the language of the interface and content as well. It is not a perfect solution, but it works.
you need to install the japanese language pack if you really want to do japanese. If you just want to occasionally have japanese on your site, you need to change the page encoding from english to a japanese encoding. This is found in the language/English/global.php file. Toward the bottom you can change the character set. For example I changed mine to: define('_CHARSET', 'EUC-JP');