Is it possible to run two different Rails apps on the same domain (using a subdirectory)?

You can do this but its easier to use a subdomain like game.mydomain.com because then you can deal with this problem using nginx. For the seperation of the different ruby and rails versions use rvm (https://rvm.io/).

Then you can create a nginx config like this:

upstream mydomain.com {        server unix:/var/run/thin/mydomain.0.sock;        server unix:/var/run/thin/mydomain.1.sock;        server unix:/var/run/thin/mydomain.2.sock;        server unix:/var/run/thin/mydomain.3.sock;}upstream game.mydomain.com {        server unix:/var/run/thin/game.mydomain.0.sock;        server unix:/var/run/thin/game.mydomain.1.sock;        server unix:/var/run/thin/game.mydomain.2.sock;        server unix:/var/run/thin/game.mydomain.3.sock;}server {        listen 80;        server_name mydomain.com;        access_log /path/to/rails/app/log/access.log;        error_log /path/to/rails/app/log/error.log;        root /path/to/rails/app/public;        index index.html;        location / {                proxy_set_header X-Real-IP $remote_addr;                proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;                proxy_set_header Host $http_host;                proxy_redirect off;                if (-f $request_filename/index.html) {                        rewrite (.*) $1/index.html break;                }                if (-f $request_filename.html) {                        rewrite (.*) $1.html break;                }                if (!-f $request_filename) {                        proxy_pass http://mydomain.com;                        break;                }        }}server {        listen 80;        server_name game.mydomain.com;        access_log /path/to/rails/app/log/access.log;        error_log /path/to/rails/app/log/error.log;        root /path/to/rails/app/public;        index index.html;        location / {                proxy_set_header X-Real-IP $remote_addr;                proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;                proxy_set_header Host $http_host;                proxy_redirect off;                if (-f $request_filename/index.html) {                        rewrite (.*) $1/index.html break;                }                if (-f $request_filename.html) {                        rewrite (.*) $1.html break;                }                if (!-f $request_filename) {                        proxy_pass http://game.mydomain.com;                        break;                }        }}

That should do it for you if its acceptable to use subdomains instead of subfolders.

If you really wanna use subdirectories you can do this using nginx locationdirective:

http://wiki.nginx.org/HttpCoreModule#location

Yes

Run it on a Sub Domain you dont want to cause problems with your existing Application.