Whenever I switch my phone on it always shows the name of rom installed, but after that my phone does not get on. I want to recover its internal data .I don't know what to do with cwm-based recovery. Can I retrieve whatsapp chats too?
Ideally you can retrieve nearly everything under CWM via ADB. Use
adb shell to explore file structure and
adb pull to pull what you want to PC.
However, 1) finding what you want to achieve can be painful, since you need to be familiar with Android filesystem structure, and ADB command line isn't friendly either; 2) even if you managed to find WhatsApp's data, you might not be able to make out what file(s) correspond to chats, and have to do a whole-folder backup, which then means restoring will be a pain (setting permissions and owners).
Retrieving contacts, SMS and simple game saves shouldn't be a problem though, as these usually are stored in one or two files. I've always backed up my savegames in a similar manner. Internal storage is also easy since you know that file structure well.