How to deploy HikaShop?

Hi,

What do you mean by "adding new functionality" ?
Most of our users have a test website (either locally or online but not accessible by others) where they prepare their website with hikashop on it. Once all setup, they move it to the production website. Some use akeeba backup for that but others just do it manually by exporting/importing their database via phpmyadmin and copy the files via FTP.

Concerning updates, there are two type of users:
the ones who make a backup and update hikashop on the production server directly.
others who make a copy of their production website on a test website and update there, test that everything is working and only then push the update to the production website.

Updates of hikashop can be installed like when you first install it. It keeps all the settings and data you already have. So it's really easy to do. Then, it depends how you handle updates in general (with pre production server or directly on your server) as I explained above.