Sakito95: Hi! I recently found an old (and in unexpectingly good condition XD) copy of the Official Guide of Pandemonium! and I think I've found the secret room in Cloud Citadel... I still haven't tried yet to do a perfect run of the level but I'm sure that this is the secret we are looking for... just look at picture #31 of the image attached and let me know if that's what you needed!

Edit: As for the Heart Containers, the Guide is clear, there's a maximum of 7 Hearts you can have, so only 5 to collect. If you got an 8th Heart after using the "Coronary" password it's probably because it works as a cheat

Sakito95: Hi! I recently found an old (and in unexpectingly good condition XD) copy of the Official Guide of Pandemonium! and I think I've found the secret room in Cloud Citadel... I still haven't tried yet to do a perfect run of the level but I'm sure that this is the secret we are looking for... just look at picture #31 of the image attached and let me know if that's what you needed!

Edit: As for the Heart Containers, the Guide is clear, there's a maximum of 7 Hearts you can have, so only 5 to collect. If you got an 8th Heart after using the "Coronary" password it's probably because it works as a cheat