How to prevent applications to donwload data automatically? I have many applications installed on my Samsung Galaxy Tab 10.1. And it always download something from internet, in order to update and upgrade applications. It does it all the day and night, when I am in my home or business WiFi and when I am in mobile network.

How to disable this "feature"? I don't want any blind upgrades, only by my explicit permission.

Also, of course, I don't want to replace numerous downloads with numerous asks for permission.
This is part of Google Play Store settings. Select Do not auto-update apps in the following path:
Google Play Store>Settings>Auto update apps>Do not auto-update apps

This is a global setting, but it may be overridden by a specific setting at the application level. For instance, an application may have a specific setting to update itself, especially if that application came from a 3rd party source. You will need to check those application settings individually and prevent auto-updating there. However, this is not generally true, in fact I think it is a violation of terms, if that application comes from the Google Play Store.