Hi Anurag,
There are no such requirements to create unmanaged package, you can create unmanaged package by following steps:-
- Type Packages in quick/find search box.
- Click on the link packages.
- Now click New button on the packages section.
- Fill the required fields and leave the Managed checkbox false. This will create your unmanaged package.
- Add components and Upload it.
Package uploads and installs are available in Group, Professional, Enterprise, Performance, Unlimited, and Developer Editions
Hope this helps.