i can answer number 4 and take a stab at number 3
number 4. YES! there are lots of chat applications gaim(does most protocols), everybuddy(does most protocols), bitchX(irc),and many many more, if you need a specific protocol go to
www.freshmeat.net and search for the name of its windows counterpart, i also think trillian works through wine but i like gaim more, if your looking for a suggestion go gaim and bitchX
number 3 i assume you mean in your file manager? there should hopefully be a option in your kde/gnome menu if your using either of those, if not then please clarify your question