Pre-sales question

Can I get Urls like this with SEF Advance?:

www.cosmo.net/ai24567.htm

Meaning what?

If your static content has a title "ai24567" and you have ".htm" suffix then you certainly can.

Yes.. The old website we are migrating has URLs like...

www.cosmo.net/ai24567.htm We want to migrate to Joomla, and keep the exact same URLs so that all the old links still work.

Can only static content items have these kinds of URLs? Or could any components, or content item have  such a URL?

Only the static content will have "first directory" form. For other content you can use manual alias.

What is "manual alias?" Does that mean I can assign any URL I want to any Joomla URL? That would be perfect.

Yes it does, but that has to be done manually for each URL.
You can read the documentation for more info or download the free trial and test.