Welcome my friend.
1) It WAS the case that most people could get into most nightclubs for free (unless you looked Cypriot, whereby you'd have to pay) .... it's becoming more the case that they're making a lot of people pay, especially on weekends.... but you can still get in for free if you find a bar dishing out the free entrances, but usually not to major clubs.... if you want free entrance to castle, try the Marinella Bar in the Square which offered us free entrancs there which only worked on certain days, but still worked eventually.... not on weekends though....
2) Absolutely positively NOT TRUE!!!!! Yiannis, things have changed.... since Cy joined the EU the prices of alcohol in the shops have really come down (though they only seem to have gone up in the bars and clubs). A bottle of Gordons gin at the local store in Limassol costs about 6 CYP and good'ol Johnnie wasnt too expensive at around 7 CYP if I remember correctly, and most alcohol was priced around this range.... of course, if you're really desperate for intoxication, you can buy a bottle of local "vodka" and other alcohol substances for the ridiculous price of 2 CYP or something, but i highly discourage you from doing so....
3) Dunno bout Techno.... probably Castle yeah cos they have 3 Arenas, the other clubs change music most days so check out the flyers to see where to go.... just skip Black'n'white (R'n'B exclusive club).... Coyote Ugly had a trancey room upstairs and entrance to that club was only 2 CYP!!!
4) What the crap is that?
You can find other stuff to do... like Yiannis said, bungee jumping, waterpark, bicycling to cape Greco or by motorbike, you can checkout Protoras and theres a nice show called "Dancing on water or ice or something like that"
I guess you can always go down to Larnaca by bus but there's really not much to see there..... other places are too far away. you can cross to the Turkish side to see Famagusta, but I don't know how you would go about doing that...... hrmmmmm dunno, ask around when you get there....