This can be done already in PB, and as such fits in the "general discussion" board.
To answer your question, let's suppose I want the player to collect all 4 password cards, then go to the computer to hack it, and then go to the exit flag.
First off, i will make the end flag using the method I told you in the last thread, except it checks if the area value "computerhacked" is = 1(we'll get back to it later).
Then, I will make a password card item that increase the area value "passcardcount" by 1 when collected.
Then I will make a computer object that when pressing up near it (that's the default interaction button for PB games), checks if value passcardcount is = 4. If yes, the interaction will be successful, the computer will be hacked, and the area value "ispchacked" will be set to 1, meaning you can use the exit flag.
If you also want the player to defeat the boss after hacking the computer and before going to the flag, and you want it to not appear until computer is hacked, you can make an event "spawn boss at spawn id [something]" when the interaction to hack the pc is successful, set the area value "bossdefeated" when defeating the boss, and make the flag check for that value instead of the "computerhacked" area value. If you want it to spawn when collecting all cards, you can make the card do also this when collected: check if the value reached 4, and if yes, spawns the boss.
Reminder tho: All area values must be defined to 0 in the begin area prompt.
Hope this helps.