This is advice on how to beat 4/20 mode and get the 100% completion, if you don't want my advice, then please don't read any further, thank you.
Ok so, I started playing this game just about 3 or 4 days ago and I managed to get the 100% completion. The only thing I have yet to see is a rumored puppet scene. However I do have some advice that might prove useful for the 4/20 mode as I somehow managed to beat it on my first try.
First, I started off by switching my camera to foxy. Only checking on her every 8-10 seconds, with no more than a flick. Then I would only switch cams if i heard Freddy laugh (This was just to make sure she wasn't on the cam closest to the office).
Next, I would listen to sound cues from bonnie and chica. You have quite a bit of time to react to their footsteps and check which side they are on via one flicker from the light ( I noticed after the first 3 times that they don't usually stay longer than a second or two, so to preserve power you can count in your head and just open the door instead of checking with the light). Also keep in mind, in case you don't already know, freddy is extremely fast and so you can complete the run by just keeping the door closed whenever she is in the room closest to the office. if you try to look for her in the hallways, it will already be too late for you.
Finally, i just keep my camera's closed, except for the few flickers, to preserve as much energy as possible. if you are lucky like me and run out of power about 10-15 seconds into 5AM, then congratulations! You just beat the night on 4/20 Mode!
After this point, you can enter the digits "1987" and "6969" respectively for the ai difficulty settings on night 7. 1987 is just a small easter egg from phone guy and is part of the 100% completion. 6969 will just activate the golden freddy crash scene which was the last thing i did to get my 100% completion. After you get 100% there is no grand scene or anything, just a picture of the 4 main girls having an orgy promising a part 2 soon. But overall, it was worth my time. I wonder if it will be worth your own?
P.S: I forgot to mention that i would close my door before activating the foxy running cutscene. This did take up a bit of energy, so if you can instead listen for the foxy sound cue of her about to enter your office and close the door on time, go for it! But I don't believe it to be necessary if you try your best with the advice above! Good Luck you degenerates! ;)