Apache: 2 SSL certificates, same DocumentRoot

If you only enter AFAIK

www.level1.mydomain.com

Enter the browser address bar and request the mydomain.com web server on port 80 http protocol. For http you don't need a certificate.

if you enter

https://www.level1.mydomain.com

You are asking on port 443/https which requires a certificate.

If you enter

level1.mydomain.com

and only configure your webserver to work with https/443, you get an error that the webserver is not listening on port 80 (502 bad gateway - or whatever).

You need to add redirects/rewrites for all domains/virtual hosts listening on https on port 80/http. It's easy - no certificate required -

like this (untested)

<VirtualHost *:80>
   ServerName level1.mydomain.com       
   Redirect / https://level1.mydomain.com
</VirtualHost>

<VirtualHost *:80>
   ServerName  www.level1.mydomain.com
   Redirect / https://level1.mydomain.com
</VirtualHost>

Type for all users

https://www.level1.mydomain.com

You just need to buy an additional certificate for that sub.sub.domain or get a free letsencrypt.org certificate to redirect. Maybe not worth the trouble.

BTW adding a second virtual host pointing to the same DocumentRoot might work for plain HTML pages, but not for applications. I will go redirect.

Tutorial on redirect/rewrite
https://www.tecmint.com/redirect-http-to-https-on-apache/

About letsencrypt
https://letsencrypt.org/