Installing Nexus Images on other devices I am absolutely noob in Android hacking, though I am quite good in doing techie stuff.

Now I have got my first mobile Karbonn A5+. It has 1GHz processor and 431 MB ROM+RAM. It runs Gingerbread. As usual it doesnt get updates.

I really want to taste JellyBean on it. So while googling for the same, I found this thread. It instructs to install clean nexus images from here. Can I able to install the same on my mobile following the same instructions?
You can only use images specifically made for your own device. Unlike common Linux Live CD images, Android images usually comes only with the drivers for the particular device it was intended for to save space. It's highly unlikely you'll be able to run an image designed for another device well, unless the hardware on the device is extremely similar to the original device. 

Many modders compiles from source code and spends a lot of time figuring out the compilation flags that excludes the drivers they don't need while making sure it includes the ones they need, and tweaking the settings to optimize it for the device; this may be difficult on some device if the manufacturers don't release all their source code or if they didn't publish the settings they used in their own images. Some modders swaps compiled modules from another device with similar hardware into a base image that is known to work on their device; this is essentially trial and error though because there's no guarantee it will work at all. In some extreme cases, there has been times where modders felt that the manufacturer has done an extremely poor job on certain driver and rewrite the entire driver from scratch.

In any of these methods, you need to be very familiar with both kernel and the hardware on the device. It's generally easier if the manufacturer released vanilla images and/or their compilation settings.

Unlike the compiled binaries, APKs are generally interchangeable though, because they are compiled in Dalvik instead of ARM. Often it's possible to get a sneak peak of later device's feature by side loading the right APKs. This is why it's often possible to install newer launchers and keyboards on previous versions of Android.