Yes, that's possible:
all sites will have exactly same Hikashop data, but each site can be configured to display specific product/products via menu items pointed to specific Hikashop views.

... will be specific to one product, the other website specific to the other, but both products are also in my main Hikashop. Is this doable to display one specific product and its variants on a seperate website - as in share a chosen product or products? Thanks

... previous document base overwrite. ⋅ New features in latest forum activity module: new setting 'Only Unread Items' which allows you to display i.e. only unread topics, and 'Show Unread Status' which highlights unread topics or posts. 'Show Replies Count' allows you to display count ...

... Each of sites can share articles and categories, so ALL articles will be always same, but each site will have own menus so you can configure it to display articles from specific category only. That's for sure if each helmet is a Joomla article.

1 - Yes, but only in stand-alone mode (phpBB is display as usual, not inside Joomla like this forum which uses wrapped mode). Wrapped mode requires specially adopted phpBB styles. 2 - Yes, you can just redirect Joomla registration to phpBB page via ...

... data from it). You can create a separate categories of items in K2, one per each site. Next you can configure K2 menu item in main site to display items from all categories, but K2 menu item in country site will display items from its category only.

... you setup any category or client in menu item settings, so you will be abele to separate reviews output per each site, and main site will just display all reviews from all categories. 3. Will the above mentioned work for the blogs as well? Relevant content for each city? So we upload content ...

You can share only ALL menus and menu items, same for article - only ALL articles. But note that each site can be configured to display only its articles: so all sites will load same categories and articles, but each site will display articles only from selected category. Menus should ...

... I have a fourth domain which is a simple joomla site consisting of a menu and articles. These are my help for our customers. At the moment I display the help of via wrapper link in the three domains mentioned above. The problem with this solution is the SEF does not work with the wrapper. ...

... data from one site, so k2 data will be always same for all sites, edit/delete/create item on any site will affect all sites (all sites will always display same k2 contents). 4. I can suggest to use 1 database for all sites but different tables prefixes.