Breif:

like a $4-$digit access code $-2337.$ The keypad is designed as below, with numbers $0-9$ and ENTER $($E$)$ and CLEAR $($C$)$ buttons. To unlock the door, the right sequence of buttons must be pressed, followed by the ENTER button. Pressing the CLEAR button will reset the entered sequence. Now, Mr Keggs realises that one could just use trial and error to unlock the door, and so if an incorrect code is entered $3$ times in a row, an alarm must sound $($until a reset is applied$).$

$//$picture for reference

What I have so far:

$//$logic diagram picture

FSM $1$:

create a state diagram, state table and flip flop equations of a finite state machine for checking the lock keypad input. The correct $4-$digit access code is $2337.$ Therefore the inputs should be only $2,3,7$ and X Where X is the and gate output of numbers $0,1,4,5,6,8,9.$

Should produce two outputs, incorrect and correct.

States are Idel, input $1,$ input $2,$ input $3$ and, input $4.$

FSM $2$:

If output of FSM $1$ is incorrect go to FSM which counts the number of incorrect codes. If $1$ or $2$ incorrect codes are counted in a row, return back to idle state in FSM $1.$ If $3$ incorrect codes are counted in a row, trigger the alarm.

FSM $3.$ if output of FSM $1$ is correct go to a counter which unlocks a door a counts to $3$ before returning to idle state in FSM $1.$