Hello Everyone.
I've did some research and I can say that the floppy bios from Sergey Kiselev is I would say in a halfway.
I'm playing now with a newly build old computer and I've decided to assemble something with multiple floppies and multiple OSes.
And yeah - I've spend almost a month on understanding what's wrong with my setpu.

First of all - main BIOS. I've tried ATC-1020, Biostar M5ATA, and Chicony CH-471B.
- You can forget about using second controller on ISA to get 4 floppy setup. You have to disable embedded controller, use quad floppy card, or two double floppy with configurable I/O. Seemingly everything works with embedded controller but 5,25 can't properly read the files. Maybe it's the matter of jumper settings on my 5,25's but those were perfectly working on build in BIOS, but fail on SK BIOS.
- You can forget of using 4 floppy setup with SK BIOS with to new main BIOS. Every time when I was burning BIOS (4.51) newer than 1997 the motor on signal was saying bye! I have no idea if this is related to different int 13h handling or simply with signal routing pattern in newer BIOSes but it always ended up like this.
- Windows 98 - forget it - it can't handle 4 floppies. You will get protection error.
- Windows 95 - if you have correct BIOS and correct cards and correct setting all you have to do is to disable standard floppy controller in device manager. FDDs are still working (all 4) and you won't get protection error anymore.
- If you have bad luck and this doesn't work then you have to set up floppy A in BIOS (keeping embedded controller disabled).
- Forget about using Sergey's BIOS with XT_IDE (IDE_386) - IDE_386's way of handling INT 13h and swapping FDDs will drive you mad . On newer BIOSes you can integrate Sergey's or XT_IDE's or both in main BIOS but then forget about using Windows 9x. On older BIOSes without fully implemented handling of ISA or PCI roms this won't work. You can successfully add those modules to the main BIOS using cbrom or awbedit but those won't be loaded into memory.

Couple words about sdrive and other drivers. The most reliable is the driver from DOS 6.22 - it's just working. Others (DC2, Sdrive, Wonder34, DOSFDRV) - if you have proper hardware can work, but many kontroler just don't want to communicate with them.

Of course still there is a lot of fun checking which particular EPROM of with particular capacity will work in ISA card and which in PCI card and so on, so forth.
Unfortunately my understanding of PC architecture is very general so I couldn't debug it properly.
All I could do was to fail and learn.

Best regards!

After some additional insight I've discovered that there is an update for IOS.VXD for Windows 95 that make it works with 4 floppies.