second form is the worst, full of woe and despair. 5th form is fully doable, like Glamador said, you take a major hit and let yourself heal up. I went for jelly costume as soon as I could on second time through and it's helped invaluably ( optional sure, if you hate yourself )
even if you read up on something, it's still technically difficult, so reading up on a spoiler dosn't totally take away from how hard something can be. some of the boss puzzles are really difficult, I gave up with Mithalis and had to read up on him and it was still freakin hard.