Yes manual only
Most often your default, however, Any page (or main section page) that matches a category.
No, and you should review DMOZ submission guidelines in order to create the best possible chance of being accepted.
In general you can receive 1 regional listing (2 if you are both a local vendor and national or international vendor) and 1 or more topical categories (e.g. a listings about your information, products or services)
multiple topical listings can occur if for example you:
1. design widgets,
2. fix widgets,
3. sell your own widgets
4. resell other vendor's widgets.
In this case four potential topical categories could be listed.
Should your web site be very diverse in topics or your web site covers multiple industries, segments or caters to multiple markets you can receive many listings in DMOZ.