Create bootable ISO from Win10 recovery USB

Hello,

I am having a unique problem and cannot find a solution in the forums or Google. Here are the specifics:

December 2015:
- Bought an HP-Stream laptop specifically to load Linux. It came with Windows 10.
- Using Win10 utilities I moved the recovery drives to a USB stick (supposed to be bootable). I reclaimed the recovery partition and loaded Linux.
- I LOVE Linux. I wish I could drop Microsoft altogether.

Today:
- Unfortunately, I have found that I still need Windows for some tasks.
- I installed VirtualBox and setup a Win10 drive.
- I am attempting to install my copy of Win10, but I'm having difficulties:
Other considerations:
- I have a Win8.1 laptop at home. I do not wish to use that computer for these tasks as that machine is my gaming laptop.
- I have no other Win10 machines.

Questions:
1. Can I convert the existing Win10 ISO to be bootable?
2. If not, can I create a bootable ISO from the Win10 recovery USB?
3. Can I use my Win8.1 laptop to create a bootable ISO from my Win10 recovery USB?
4. Can I use a different bootable ISO (any OS) to boot the VM, then load Win10? Or must I boot with Win10 to install it?

Any help is greatly appreciated.
Thank you for your time.
Shawn