Accessing Flask WS APIs over intranet -
1) YES. the updates won't be visible not until your restart your webservice. ( Both by the way ).

2) Gunicorn works well with Flask as a wsgi app. I'm not sure how to answer your question. All i can say is that i have webservices deployed to production with both Gunicorn+ Flask and Flask only, and they are both accessible over internet. Only difference is that Flask is not meant for production deployment, only for testing purposes.