1) As I said, it depends on your level of coding knowledge as to what you can do for yourself. But what I'm saying is that what you're asking is not controlled by standard settings in the ClassiPress admin. There are various mods shared in the forums by other members of the community so sometimes you can find existing thread to assist with changes, otherwise you can also seek community based support if you wish to ask further questions. Customizations are not officially supported.
2) You have to appreciate that we have thousands of customers and it's not possible to simply add features/functions as soon as someone comes along and wants to see something added. This is why we have the
AppThemes Ideas Exchange, so our community can post feature requests, and others can vote. This way our development team have a better idea of what the overall community wants.
3) Basically, if you customize the default theme, and a new version of the theme is released, then yes you should expect to lose changes you have made to the theme files, although you won't lose actual settings and logos. The way to minimize this is to create a
child theme, and note that our themes come with patch releases which allows you to change only those files that have been updated since the last version.
In terms of your last post, if you're planning to make changes that don't effect all users and is selective on who is logged in, this will take some customization as usually such changes do effect everyone. So, to say it's possible, yes, but whether or not you yourself can make the customization is really up to you.