Hi,
When you renew your subscription you can download both v5 and v7 from your account.
Acyba is completely recoding Acymailing and that became version 6. After a major change in v6 they changed the version number into 7, but in fact it is an ongoing development of v6.
V5 and v7 each use their own set of database tables. So you can install both on your site. That way you can continue to use v5 and start to get familiar with v7. Make sure you attach your license to v5 and whenever you start using v7 in production you can unlink your license from v5 and link it to v7 instead.
Please be aware that Acyba has stopped developing v5. Currently they only provide bug fixes and at some point they will stop that providing these as well. The future of Acymailing is at v7.
You'll find all the v7 documentation here: https://docs.acymailing.com/.
The v5 mass actions are in v7 located under the menu item Automations. There you can run your one time mass actions and if you have regular mass actions to run you can even automate that in an automation. It's documented here: https://docs.acymailing.com/main-pages/automations.
Instead of the v5 plugins v7 is using add-ons. You can easily add them from within Acymailing. The Universal filter you refer to is also available as an add-on. It's all doucmenteded here https://docs.acymailing.com/main-pages/add-ons and here https://docs.acymailing.com/addons/all-cms-add-ons/universal-filter.