Wildcard Subdomain Location Issue

I created wordpress multisite with wildcard subdomain.

Wildcard Subdomain is: *.domain.com
Document Root is: home/public_html

I created a geo-specific subdomain site under network admin settings: abc.domain.com

1. Should I change subdomain’s location to something else?
Eg: home/public_html/abc

2. Since all the themes and plugins are same and located at the same location, would changing setting in subdomain dashboard (of plugins and theme), change settings in main domain also?
Eg: I am using woocommerce plugin on both domain and subdomain. I have been using main domain since a long time and it had installed plugin specific php files in the theme, during first use. I had changed a few codes in those files to suit my needs and it is working properly.
Now, in subdomain, it is again asking to install those php files. Wouldn’t this change the original files?

3. I wish to use same images for both domain and subdomain, without duplicating them.
I tried creating symbolic link using command in shell:
ln -s /path/to/images /path/to/subdomain/images
(in my case: ln -s public_html/wp-content/uploads public_html/wp-content/uploads/sites/3)
After pressing enter, no error or success message was shown and new line for new command was displayed.
(On retrying the command, ln: creating symbolic link public_html/wp-content/uploads/sites/3/uploads: File exists)
And in media tab of subdomain dashboard, I still can’t see of my main domain’s images.
I tried using Network Shared Media plugin. But it doesn’t work, if you want to add pictures to the products.
What should I do?
(I am on linux hosting, using puTTy in windows to access SSH)