Welcome :)
1) You should use roms labeled as "[!]" in the
GoodXXX sets. They are perfect dumps. When there are more versions, such as "J", "E", "U", which stands for Japan, Europe, USA, you should choose wisely. European roms run at 50Hz so they're not a good choice as a rule of thumb. Japanese roms may have unreadable text, but sometimes there are bugs and glitches that work only in them. It's a good thing to discuss the rom version beforehand in the
discussion forums if you need some specific advices. Also, hacks aren't welcome, and exceptions are rarely granted.
One more thing, please note that you can't ask for roms on this forum. So you should edit your post to blank out that request.
2) You must record from start, without savestates if the game makes use of them (e.g. an RPG that saves your progress and your stats). It must be like you're playing the game for the first time. There is no clear rule about the ending point instead, but once the movie is finished, you must ensure that the game gets to the last screen in the game without further input, might it be a "The End" screen or a "Game Over" screen.
3) Emulators and NesVideoAgent calculate that by counting the frames recorded.
4) See 2.
5) You don't submit an AVI (or MKV) file to tasvideos.org, you submit your recording (file.smv), zipped. Then a qualified encoder will make an AVI (or MKV), but only if your speedrun is good enough to be published. There is a number of people (including me) who make encodes of the movies in the workbench sometimes though.
I hope this can be of some help :)
A birthday present I got some time ago. So new I didn't even remove the "large" sticker :P