I uninstalled everything and started the work again this time this way:
On my Windows 7 x64, I installed:
qt-opensource-windows-x86-android-5.7.0 (I thought the problem may be of 5.8 so installed this time 5.7)
android-studio-bundle-145.3537739-windows (Android Studio 2.2.3)
android-ndk-r13b
apache-ant-1.10.1
jdk-8u121-windows-x64
And after setting the Android Tab of Qt Creator 5.7, I ran SDK Manager using its path:C:\Users\CS\AppData\Local\Android\sdk
Result: http://imgur.com/a/CLZZu
Once again, this time using a Windows 10 x64 virtual machine, I installed:
qt-opensource-windows-x86-android-5.8.0
android-studio-bundle-145.3537739-windows (Android Studio 2.2.3)
android-ndk-r13b
apache-ant-1.10.1
jdk-8u121-windows-x64
And after setting the Android Tab of Qt Creator 5.8, I ran SDK Manager using its path: C:\Users\CS\AppData\Local\Android\sdk
Result: http://imgur.com/a/WAuCe
They are unfortunately the same.
So the problem is not of the operating system.
I don't know if I had gone the way wrongly somewhere. But it's so strange.
I think there maybe a problem with Android Studio 2.2.3. Probably I should test a lower version, 2.2.2 to be able to install the required packages. :-( :-( :-(