Install and Boot Windows 10 with UEFI and FreeBSD with Legacy

Hi :)
For using Windows 10 at work and FreeBSD at home with my laptop on real hardware, I intend to create two primary partitions on HDD: one for Windows 10 and the other for FreeBSD.

Observations:

  1. My laptop has secure boot enabled and it is not possible to disable it on Acer’s bios setup “InsydeH20”, so the mini-memstick.img only boots with Legacy.
  2. The product key is stored in BIOS and will be used automatically by Windows 10 when connected to the Internet, so activation isn’t a problem.
  3. HDD’s size is 932G.

Questions:

  1. Is it possible to install and boot Windows 10 with UEFI on one partition and FreeBSD with Legacy on the other partition?

  2. If the answer for 1. is yes, then for using a web browser, a torrent client, video and music players, games that are not resource hungry, software of work and a VM on Windows 10 and for using FreeBSD's base system, what is the recommended size for each partition?
Thanks in advance!
 
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Is it possible to install and boot Windows 10 with UEFI on one partition and FreeBSD with Legacy on the other partition?

Despite:

  • booting a MBR disk with UEFI is possible, flagging the MBR sector as MBR partition type for the "EFI system partition" (0xEF)
  • booting a GPT disk in BIOS is possible too, thanks to the protective MBR s located at lba0
That is to be discouraged because:
  • chances are high you'll run into major issues, especially in the second case, with a GPT disk on BIOS or CSM/Legacy_BIOS mode
  • One one hand Microsoft does not allow booting Windows from a GPT partition table in BIOS,or with BIOS mode enabled. On the other hand, if booting Windows on a MBR disk, the install wizard will automatically and forcibly try to make a EFI partition and install the Windows boot manager on the latter, instead of appending the partition scheme to the MBR and install the Windows boot Manager to your C:\ partition
Hence, albeit being feasible (and risky) with other OSs, it's not possible with Windows unfortunately

Possible solution: if you are so lucky your motherboard supports CoreBoot (rare occurence), replace your UEFI with Coreboot + TianoCore as payload, and dual-boot Windows+FreeBSD in UEFI mode (Tianocore emulates UEFI) on a GPT PT using Grub2 as bootloader from FreeBSD.

Alternatively use SeaBIOS as payload for Coreboot, in order to dual boot FreeBSD+Windows in Legacy_BIOS mode, then use EasyBCD as bootloader from Windows system partition (EasyBCD does not work on UEFI,so can't be used with Tianocore)
 
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