[help!!!]"encryption unsuccessful" after flash CM11 over CM12.1.

My nook hd plus was working fine with cm-11-20150824 and TWRP recovery 2.7.1.0. Then I followed the thread of Unofficial CM12.1 and successfully updated to CM12.1 and TWRP 2.8.7.4. After that I decided to go back to CM11 with TWRP and my previous backup by TWRP. Then very time when I flashed CM11, after booting, the screen shows "encryption unsuccessful........." Now I can only flash back CM12.1 and it is working fine, but how can I go back to CM11?

Offline system images & packages installation unsuccessful [Eclipse/Android SDK/Java]

I am currently setting up Android SDK, eclipse and Java JDK for app development. Am fairly new to it so am not familiar with very technical jargons. I have managed to successfully setup Java JDK offline and eclipse partially. I say partially because I have been able to get it to recognize platforms, platform tools and build tools by creating recognizable folders and extracting the zip contents into them. I have not succeeded for the system images as I don't know what folder naming is requires for them to be recognized as installed in the android-sdk folder. My pc is currently located in a area where there is no cable or broadband internet since the facility is fairly new but 4G data is available but very expensive.

I tried the tutorial where you create a temp folder in android-sdk, then connect to 4G just to get the SDK manager to read the necessary packages, then disconnect, then run install packages so that it now sources them locally from the temp folder but it fails to install.

The packages I need installed but dont have their zips for offline installation are:-

- Android SDK Build-tools, revision 23.0.1
- Documentation for Android SDK, API 23, revision 1
- SDK Platform Android 6.0, API 23, revision 1
- Samples for SDK API 23, revision 2
- Android TV ARM EABI v7a System Image, Android API 23, revision 2
- Android TV Intel x86 Atom System Image, Android API 23, revision 2
- ARM EABI v7a System Image, Android API 23, revision 3
- Intel x86 Atom_64 System Image, Android API 23, revision 3
- Intel x86 Atom System Image, Android API 23, revision 3
- Google APIs, Android API 23, revision 1
- Google APIs ARM EABI v7a System Image, Google Inc. API 23, revision 7
- Google APIs Intel x86 Atom_64 System Image, Google Inc. API 23, revision 7
- Google APIs Intel x86 Atom System Image, Google Inc. API 23, revision 7
- Sources for Android SDK, API 23, revision 1
- Android Support Library, revision 23.0.1
- Google USB Driver, revision 11


Can anyone provide me with these zips and what folders to create in the android-sdk folder to get them installed?