Hi. I previously had one of my hdds (the 2nd one) mapped as one big extended partition with 3 logical ntfs drives. Recently i had "converted" all my ntfs partitions from the extended one in ext4. The extended partition remained the same type. Is it another linux-specific extended partition (container) type or it's just a standard one? (because i don't like the idea of having linux partition in a windows container).

The extended partition is labeled as win95 extended, but it imposes no windows formatting on the logical partition contained within the extended partition. You don't need to worry about that.

If I'm not sorely mistaken, it's also related to BIOS issues.

However, you may want to investigate coreboot (formerly know as linuxbios) as a freeware replacement for proprietary BIOS firmware. If your motherboard and chipset are supported, you may want to replace you current BIOS with coreboot. It is suposed to greatly reduce boot time. Whether or not it changes the extended partition issue I don't know.