Thanks for the replies guys!
By un brick able you mean that its hard to brick it, or if I brick it its hard to un brick (fix) it then?
Also I'm having a hard understanding, if kernel is the thing that manages the hardware and also responsible for lagfix then kernel is really what matters for the performance of the phone. How a ROM could improve phones performance?
Also one more questions:
As I understand CSC and modem are connectivity related files (3G internet, APNS etc) right? So its better not to touch them when flashing custom ROM/kernel?
Thanks a lot again!
Actually the kernel is a part of a ROM. So ROM is the necessary requirement along with kernel basically they complement each other