dispaly a sub menu according to plan

I am intending to have 3 plans one running for 3 months, one for 6 and one for 12, at different prices; how can I display a different submenu for each;
can a renewal keep access to the resouces it had initially? [- essentoially an upgrade to the next level of plan?]

Different submenu? Can you be more specific? You're wanting to conditionally display Joomla menus?

well, I wanted each plan to have it's own sidebar menus; I now remember  how to do it by using the conent p[lug-in and selecting the required menus
sorry - it's been a long while (10 yuears?) since I set up a site like the one I'm working on.
I guess that the only way to control access to categories is to select the articles in each category individually, as they are created?
 

Ok, for that then I'd just have different menu modules for each plan then within your plans under Integrations > Extensions protect the menu module relevant to each plan. That should do the trick.

For content categories you can either select them manually under Integrations > Content of your plans or use By URL Part protection under Integrations > Extensions and protect REGEXP supported URLs (uses non-SEO URLs here!) to protect basically an infinite amount of categories dynamically.

Another way to protect menu modules, menu items, or even content categories is to just use ACL. Create a usergroup for each plan. Something like the below structure.

- Registered
- - Beginner
- - Professional

Next configure each plan under Access to give their relevant usergroup. Now create View Access Levels for those usergroups. Finally you can just protect content through your site entirely through Joomla ACL.