Developed on a bpn network subdomain, the link would look like this:
[your site name].bpn.network
This work is done by bpn, however, a login can be provided if you prefer a more hands-on approach.
The prototype can be exported into one file that can be archived or migrated to another network. The prototype sub-domain link is kept active after launch to provide a place to do any future development or testing without disrupting your live site.