On question 1:
There are probably two answers to this. The simple one is that if it's in a built up area (over 1500 pop.? i.e. more than a village) it's urban, otherwise it's rural. I'm taking the figure of 1500 from the 2000 Act re Local Area Plans- it's the threshold beyond which a plan is required. (Check the figure to be sure.) Or more simply- can you see more green than grey?:)
The second answer is that every part of the country is covered by a county development plan drawn up by a planning authority, but only certain parts are covered by special urban plans- scheduled towns in a county DP, discrete town DPs made by UDCs etc. So if a site's not covered by a town plan, it's probably rural.
Have you asked the planning authority in question? They should know for sure.
On question 2:
I have a vague memory that this was discussed in a previous thread, but I can't remember which one. Probably in this 'Irish Planning Matters' sub-forum. If you do a search for 'validation/valid/invalid' (try a few possibilities) in the blue bar near the top of the page (see above, between 'New Posts; and 'Quick Links') it should turn up the relevant info.
My gut feeling is that once it's been validated it's in the clear, but I've a niggling feeling that I'm wrong too. Certainly, it would be better to have it validated properly so ther are no hiccups down the line.
One other thing- I have a faint memory of something like this going through the courts recently, where the issue of validation was the core of the case. You don't want a high court challenge on your hands now, do you?;)
Sorry for the lack of certainty. It's been a long day and my head is a little woolly.
Maybe someone else could confirm/deny- sw101?