addon domains (subdomains) and subdirectories

Hello there,

Thanks for putting this up for us here in the community.

Please, I would be really grateful if you could help me with a couple of concerns:

I would use this for two sites and 3 wp installations I have on shared hosting (hostgator). My sites’s structure is:

https://maindomain.com
https://addondomain1.maindomain.com (which is publicly accessible at https://addondomain1.com)
https://adondomain1.com/subdirectory.maindomain.com (which is publicly accessible at https://addondmain1/subdirectory

My concerns are:

1) if I install the plugin in https://maindomain.com and I obtain a certificate from there, will my other site (https://addondomain1.maindomain.com) also automatically use the same certificate? and my subdirectory at https://addondomain1/subdirectory.maindomain.com?

2) Or will I need to install the plugin in all 3 wp installations?

3) Even if one installation in the main domain were enough in order to have a certificate for the other sites in the subdomain and in the subdirectory within the subdomain, would I need to upload the code provided by letsencrypt to the 3 different locations, those for each of my wp installations?

Many thanks!