Um, try again in english? Maybe including what you want to do?
There are no particular modifications for the BC-248CLT, other than general ones like adding audio jacks or the like.
No, you can't 'unlock' bands that aren't in a scanner. The 248 is low, high, and UHF only, no 800 MHz. Very, very obsolete, unless you happen to live in an area where there is no 800 MHz use by the people you want to listen to.