I tried installing FreeBSD 12 release version on my system which already had 3 Linux OS installed. It was the minimal install iso image. My internal HDD with GPT partition table. I tried using the ZFS file system for the FreeBSD and GRUB2 bootloader configured from the first OS which is Arch Linux. Didn't know about this issue with Linux system and GRUB not supporting/recognising ZFS file system by default. GRUB wouldn't recognise ZFS file system and hence wouldn't boot it. While trying some tweaks from the Grub Shell to boot FreeBSD I ended up wiping my hard disk.
Edit: Whàt is the best way to dual boot Linux and FreeBSD on the same Hard disk preferably with GRUB2 bootloader ? Emphasis being on the file system for FreeBSD in a such a scenario.