tamper problem?

hello, i need to install two new sensors and remove one door contact in my house and need help on how to install the sensors the remove the door contact from the main control panel. the alarm is accenta g3 with a built in keypad. How do you deactivate a sensor while the rest sensors are still on. for the sensors i will need 6 core right? I also own a shop and getting a extension done but the builders i think has cut the a sensor wire the system has gone to tamper and somehow cannot come out i have tried resetting the alarm and still no change.How do i fix it can i remove the but that has been cut and use a connector to join the rest the alarm is the same as mine accenta g3 with built in keypad.