If you're not paying for a CC Subscription, you can always just email the illustration to someone at work, or save it to your device, then transfer it as a PNG file.
I've been in your shoes - well almost. Before I started to create something with my own account, I asked the studio to assign me one of their Team licenses. That way, you can save it to your Team Account instead of your personal account.
Alternatively, if the studio you're at is going to expect you to use your personal account to create illustrations, you should ask them to purchase a CC subscription for you. They can do it month-to-month while you need it.
They get the artwork you created (for about $19/mo), and you can use either Photoshop or Illustrator, plus 20G of space.
If it's only for Photoshop, it's just around $9
1) You should be able to save the flattened image to Photos. Tap the share icon (box with arrow), > "... Share" > "Save image". This will export the current image to Camera Roll.
The ID problem however isn't entirely clear to me. If You have an Adobe ID, and a different Behance ID, and feel that is the problem: you can link them; or rather change associations and basically use one ID only for Behance AND Adobe. See here How do I change the email address associated with my account? – Behance Helpcenter
Hope that helps,
I just want to make sure I'm understanding.... You have two accounts? One with your work in it. And another that's linked to a Creative Cloud account (does that account have access to the Creative Cloud desktop software)?
Let me know because there are ways you can share the work with yourself, but it sounds like you're going to want to be able to get it onto the desktop and I can't determine whether you have that ability.