Actually, I believe I know all 4 except #3 which might be a mistake.
1
Ultimate Kuroha
It's a fusion with 4500 ATK and 3800 DEF. It's obviously Blue-Eyes Ultimate Dragon and related cards in Seto Kaiba's deck like Blue-Eyes Alternative Ultimate Dragon, Neo Blue-Eyes Ultimate Dragon, et al.
2
Pure Kuroha
Less obvious but looking up ATK 2000 and DEF 1700 gives Dark Magician Girl and related cards in Yugi's / Atem's deck like Apprentice Illusion Magician, Toon Dark Magician Girl, Palladium Oracle Mana, et al.
3
(we'll get to this next)
4
Alter Kuroha
It's an illusion monster with 0 ATK and 0 DEF. It's Relinquished or related cards in Maximillion Pegasus's deck like Thousand-Eyes Idol, Thousand-Eyes Restrict, Dark-Eyes Illusionist (at least in the anime), Millennium-Eyes Restrict, et al.
3
Sergeant Kuroha
This may be beyond generation 1 yu-gi-oh! My best bet is that it's a mistake that it should be 2000 DEF instead of 1000 DEF even if it's 2500 ATK s.t. this represents Elemental Hero Neos from generation 2 Yu-Gi-Oh! GX.
The 2500 ATK and 1000 DEF database gives this. Maybe if it's GX, then it's Elemental HERO Neos Knight.
Gen 1 cards include Guardian Grarl, Krystal Dragon, Wattaildragon. Maybe Guardian Grarl.
Or maybe it should be 2100 DEF, so it's Dark Magician.