Case 1
I think what you are trying to do is to find out what your ip, google whatismyip the top 5 will tell you what your IP is. The main thing is to do port forwarding, making whatever you are offering is possible/accessible remotely or outside of your own network.

Case2
In linksys, there is configuration that you can. Since you provide very little information about your linksys and asking an odd question that I couldn’t figure why would you expose to the world threat!