A. Yes, you can!
In most cases, assigning a DOI does not preclude submission to journals. Most journals accept submissions that have been published as preprints.
That said, it is best to double check on the Sherpa/Romeo site for specific copyright and self-archiving policies of your journal.
So, after you check the requirements of your journal, you can publish on Authorea as preprint and then submit to it. If you get published in that journal, we will update the preprint on Authorea to link to the final, published version of your article, so your final citation count won't be affected.
Published on: 05 / 13 / 2019