Should I be able to boot any ISO with pxelinux?

I have downloaded some ISO file for linux (actually from here: http://minimal.linux-bg.org/download/2018/) The I have configured it with PXE: LABEL minimallinux MENU LABEL Minimal Linux KERNEL vmlinuz INITRD /iso/minimal_linux_live_28-Jan-2018_64-bit_bios.iso APPEND iso raw and got hang or kernel panic. I was able to boot a lot of ISO-s this way. And I see on booting computer that kernel is downloaded ok, ISO is downloaded and pritouts starting. Should I be able to boot any ISO this way? If not, then what are requirements for it? What are "bios", "uefi" and "mixed" types? Isn't ISO just a container of files, which are mounted as r/o filesystem? How it can depend on it? *** I was able to boot with KERNEL memdisk where memdisk is a binary from syslinux package. What did I do? Where is Linux kernel then? Was it booted from inside ISO on later stages or it memdisk is a kernel?