My Asus K451L ( Intel® Core™ i5-4200U ) laptop was 1 year old and i want to turbo up it from 1.6ghz to 2.6ghz. Is it a good idea? If so what are the procedure and price for doing it? Newbie here
Your help is appreciate !

generally a laptop BIOS and heat equipment is not equipped for this kind of overclocking.

I tried mine, i couldn't do it since my BIOS is locked. (well, but then again, it's Dell, kinda expected) You will have to flash your BIOS with a custom unlocked BIOS if yours is locked, and there's a possibility of bricking your laptop if done wrongly or if you used the wrong BIOS for flashing.

And i think it's too high of an aim for a laptop. The heat load will instantly fry your laptop. You better aim for lower than 2.0 GHz, and even if you succeed, the heat overdose may prove to be disastrous in the long run.

I would suggest to do physical upgrades like RAM or hard drive upgrades instead. (IF you did both: Do a RAM disk: slow bootup time, but amazing fast loading times otherwise)