Well, I've found some more at Ch7.
1) Alfred has 2 banned items: Emerald javelin and shield of nature.
2) When I fought Groxts at his 2-nd phase, he turned into fireballs, I dodged them, they all swarmed at 2 big fireballs, but didn't reappear as Groxts. I stepped by Fradz into one of that huge balls, it exploded, boss appeared, but I've lost all my lives (I had 7!), and a text appeared several times "vitality 0\0". When after a while, he did that move again, fireballs worked normally.
3) When I killed him and skipped the cinematic, a small window, where boss hp, mana nd name are usually showed, appeared in all cinematics since then - Groxts, hp -0, mana -0.