I saw that some people were having trouble with night 5/6 and most couldn't complete 4/20 mode. I decided to create this account just to detail how I completed 4/20 mode in the hope that this can help someone that is stuck and wants to 100% the game.
However, if you are trying to complete 4/20 just for the final image, then I would probably say that it's not worth wasting your time. Finishing 4/20 should be for those that want the challenge and that have some time to spare. The reward for completing 4/20 mode is just that, completing the hardest possible night. To me, the final image is just a bonus reward for your achievement.
How to win 4/20 mode:
- Let's start with the easy 2: Bonnie and Chica. Not much to say really, they are quite similar. Goes without saying but don't waste power in searching for them in the cams. If you hear footsteps, check one of the doors: if one of them is there, close it. Otherwise close the other door. In 4/20 mode, they usually don't stay for long. Bonnie seems to reach your office quicker than Chica.
- Now the hard 2: Foxy and Freddy. Except Freddy is actually easy and you barely have to manage her when using this strategy. What I did to complete 4/20 was control when Foxy attacked. Using this strategy, Foxy should attack around 2am and after 4am (if you get good RNG). Start the night, open the tablet and go to Foxy's cam. Check her cam for 3-6 seconds. Close the tablet, manage Bonnie/Chica if they are at your doors and check Foxy again. Rinse and repeat. Don't be afraid to look at Foxy's cam for a long time and waste power, just make sure that you delay her attack until 2am. When you have around 60-50% power, start saving a bit of power by not looking that much at Foxy and force her to attack, which should be around 2am. When she is no longer at her cove, close the tablet and wait for her to come. DO NOT LOOK AT CAM 2a (Left Hallway) since it forces her to attack earlier than needed. When you hear her footsteps, close the door. Use this method for her second attack, which should come some time after 4am when you have around 25-15% power. If you delay her correctly, her second attack should be before Freddy finally reaches cam 6 (some time after 4am). When that happens, you open the tablet, put it on cam 6 and close the tablet. And that's Freddy and Foxy (hopefully) done. You don't need to close the door for Freddy or look at her in cam 6. While the tablet is at cam 6 (does not need to be open), Freddy will not attack you. All you need to do now is wait, defend against Bonnie and Chica and hope that Foxy does not attack a 3rd time (be ready to click the door button, just in case). If you delay Foxy correctly and have good RNG, you should run out of power some time after 5am. After that you have to hope that you get good RNG with Freddy.
Is this the best strategy? Probably not. But it's a strategy where you don't have to manage Freddy that much and that has allowed me to completed 4/20 two times already. Sorry for the wall of text but I do hope that it does help someone, even if they use a different strategy. Have fun!