I presume you mean on the PC as the X-BOX and PS3 versions are lacking, but you require a "premium" Steam account.
Steam is the program you launch Team Fortress 2 inside,
If you have bought 0 games on Steam then you can only add a certain amount of people as friends, to do this you would click ALT+TAB (default) and then click "View Players" then click "Profile" next to someones name and click "Add Friend" on their profile page.
If you haven't bought anything on Steam then your account will remain as a free account and can only add so many people, this cannot be changed.
Reason behind this:
Steam is a gaming platform client where you buy games, not a chatting service.
No, TF2 does not have any single-player. You can play on servers with random people or your steam friends
Yes. TF2 is a GREAT game, and I recommend you "buy" it. TF2 is now free to Play.
TF2 is free-to-play
No, TF2 is not playable on a phone
Hahahaha... you're thinking about gaming on a Mac? Seriously though; Yeah you could, but it's not reccomended because it's a mac.
No you cannot trade weapons for beta tf2 to normal tf2. Beta Tf2 is considered to be a completely different game by steam. Therefore the two game's inventories are not compatible.
The heavy's name in TF2 is Dimitri Stanlevkov.
Try lowering your graphics settings.
mw3 is awesome very awesome for awesome people and this stupid tf2, the gun suck, everything in tf2 is suckish. play mw3, mw3 is the best and tf2 are for noobs and losers
Weapons cannot be "leveled up" in TF2
Download it from one the many places on the internet; Place the map inside: C:\Programfiles\Steam\Steamapps\YourName\TF2\TF2\Maps
you can find the transcripts from the "Meet The..." series on the tf2 wiki.