At first, more info can be found here: https://docs.mendix.com/developerportal/deploy/mendix-cloud-deploy/#free-app
Summary for your questions
Free apps are only useful for development and playing around. If you want to use a Mendix for business purposes. Buy a licence. the limitations of a free app are not really related to your questioned parameters. But the following:
https://www.mendix.com/pricing/
If you need a simple app for a few users, without a tremendous data size a basic app for 52,50 a month is a fine license.
If the wish is to build multiple apps, for a reasonable amount of different users, big datasets etc...
Then don't think in context of apps, single licenses etc. Think of Mendix as a full application delivery and governance platform. Then the discussion isn't about what do I pay for a single license, but how can the Mendix platform support our business?
Feel free to drop me a line if you like to discuss it more