That “Live link” is from ngrok and creates a secure tunnel for others to access your files (eg. your site). It works through the web so you can just send the link provided after you click “Enable” and they can enter <your-tunnel-hash>.ngrok.io/wp-admin and login 
Note that ngrok tunneling is very slow at most cases because your computer is providing the connection and serving the files, it goes through a long way to mask your IP. The intention for that is mostly to share the website, but it should work for loading wp-admin too.
EDIT
About the “too many connections” try disabling and enabling it again (it gives you a new address every time). If that doesn’t solve it, there’s this question that talks about it:
A good workflow for this is definitely to have all 3 setups: production (or live site), staging and local. You could send that staging site for that person since there would be nothing on production.
Other than that, you can have the person to install Local and the website you are developing locally on their machine and work from there. If your development doesn’t change anything on the database, they can send you a database dump after making the changes, and you can apply it on your website.
By the way, you can export websites easily on Local clicking he right mouse button on the website you want to export and clicking “Export”, it generates a single file that can be easily imported in Local as well.
It really isn’t the optimal solution, but there’s not a good enough solution without your website being on a full server. Teamviewer and alikes will not let you work on your site at the same time as well… So using a server for this is almost the only solution (for me). Maybe you can try to use a free hosting service? Just to sort out the plugin issues.