I don't know about the complexity you are trying to build into the lock but the most simple answer would be to wire 4 digits of the lock in series to light up the LED, all the other switches can be connected in parallel to switch on an alarm. This would have the disadvantage of not having a particular sequence of the order of switches, but by utilising SPDT switches that can be made.
If u want to make the circuit using pushbuttons then a digital circuit can be designed. To latch the switch presses and take the appropriate decision. But 1st u have to make the choice about the type of sytem u want.