Update file size ? Mobile-Joomla.2.1.52.tar.gz

Mobile-Joomla.2.1.52.tar.gz -
0,48 Mb
and Mobile-Joomla.2.1.10.tar.gz - 2,2 Mb - Why? What has changed? Has something been removed?

Yes, the Mobile_Basic template is shipped separately since 2.1.49.
Previously, the Mobile Joomla package contained three versions of the Mobile_Basic template (for Joomla! 1.5, 2.5, and 3.x).

Not quite clear. Now the component and the Mobile_Basic template need to be installed separately? Has the template become paid? How to download it?

The Mobile Joomla (MJ) extension can be used to improve responsive websites as well, and in this case no extra mobile template is necessary. So, at the end of installation, MJ displays an option to one-click install Mobile_Basic template. If it is installed, internal MJ autoupdater will update this template as well. So, there is no difference with previous versions except of one optional click to install mobile template.