[BirdOPrey5]

Asking the question when they register is easy and vBulletin has a built in way of doing this.

Showing "Proxy User" in each post if they answered yes is also fairly easy to custom code, there are a number posts/guides here of how to show custom profile information in the postbit.

Showing the country they are posting from is possible but much more complicated. You will either need to edit an existing mod (there is one that shows the country flag I believe) or design a new one- you will have to download a library from somewhere that lists the IP addresses ranges for each country, there is no simple PHP or vBulletin function built in to figure out the user's country by IP address.

So it's all possible to do yes, but getting the country would likely be beyond the ability of someone with no existing PHP experience.