Thanks God I got it sorted...thanks for the help of some guys in VillainROM thread.
Actually, what happened was that after flashing Chainfire's kernel, to get rid of the Yellow triangle, I was supposed to flash the Samsung stock kernel. That's what I did. BUT, after that you had to further extract the same CHAINFIRE's kernel, NOT the stock kernel to its zImage and had to put it on the root of the internal sd_card.
But, unfortunately, I being, careless extracted Samsung's stock kernel to its zImage and copied that to the sd_card. Now after flashing Samsung's stock kernel to remove the yellow triangle, it's important to flash the ChainFire's kernel's zImage so that it could again ROOT, install busy box and add CWM on the phone.
So, guys if you still having the same problem, remove the zImage you already have on your sd_card and replace it with the 1 from ChainFire's kernel and it will sort your problem and you will be able to see CWM again with FULL options.
Samsung Galaxy S2
The best JB ROM around with great battery timing and smooth buttery experience
Half Illusion ....
If it was of any help, just hit the 'Thanks' button >>>↘