Essentially, if you're using Cloud products then there is no real 'versioning', as there are small updates and changes made very frequently (every few days), so the version changes frequently. This is different to Server/Data Center, which has a more refined list of versions you could be using.
So as Nic says in the linked post, the current version of Cloud is basically just 'Cloud', and will always be the most up to date version of itself
Your web address URL is just the https://[yourdomain].atlassian.net you're using to access your Jira Cloud site
For the email address, presumably this just means the email which you are signed up to Jira with. If you don't know this then you should go to your account icon in the top right, then Account Settings, and it will be towards the bottom of the page
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