I haven't personally investigated or tested any of the following, but a quick Google search for Joomla OTP verification revealed:
As @Sharky said, you can check the extension versions by accessing their manifest files. Here are the path of those files for each type of extension :
As Sharky says, if you don't have administrator access to the database, the best way to find out this information is from the publicly accessible files on the website such as the xml manifest files. The security on some websites does not permit you to view these files so this method is not always reliable.
Even when you do have access to the manifest files, ...
* Update *
I posted this answer and then later checked the answers by Sharky and later, Neil Roberts, saying the .xml files are available. I tested this on one of my sites, so I was very surprised that this information is available and I will have to do something about that.
I have left my original answer here for general reference and voted up the Answers ...
If you're not an administrator of the site, you can't have this information in full. If you know which extensions are installed, you can check their versions by accessing their manifest files. For example, you can find out Joomla! version by accessing administrator/manifests/files/joomla.xml file.
The closest you can get to finding out which extensions are ...
the extension is an aggregate of modules, plugins and components?
A extension, is not the combination of a component, module and plugin. This is what a package is
Plugins, Modules, Components, Templates are all types of extensions.
So if I'm right, than modules, plugins and components have the same versions. Is it also true?
No. They're all separate, ...