1. To rename tabs you need to edit the language files. Instructions here.
2. One way to list ALL members at once would be to set the option "Users page length:" under Admin > Lists menu to something really high. Cram in as many columns as you can fit, e.g. 4 or 5, then having something like 100 ro 200 users per column.
If that's not satisfactory you will need to develop a page plugin to fetch the entire user list and display it how you want to do it.
3. For birthday/age you can add profile fields in the Admin > Users menu.
