If There Is 2 Version In Play Store, How To Download An App's Other Version If there are 2 version in any App's Play store console (for 2.3 and 4.0), how can I download 2.3 version in my Android 4.0+ device?
No. You cannot do that directly. Playstore will automatically detect your Android version and gives your Most suitable version. In your case, You cannot download 2.3 version directly to your phone. However there are otherways to get that


Find a device with Android 3.0 or less. Download &amp; Install  the app from Playstore. Use apps like 'ES File manager'(Or similar apps) to get the apk of your app, Transfer via Bluetooth &amp; Install on your Android 4.0 device
Download &amp; Install Android  2.3 Emulator on your Computer &amp; Follow the same steps above.
Use www.4shared.com or Torrents or Third party app stores To download apk of the specific version of the app.