The most rewarding way to do it is the actually play the game and earn them honestly. However if you want to unlock the weapons quicker, which I don't blame you for, then join an achievement server and go at it for a couple of hours, soon you will have them all unlocked, but remember to help the others in that server get their unlocks as well!
Get achievements...
Yes. TF2 is a GREAT game, and I recommend you "buy" it. TF2 is now free to Play.
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.
Try lowering your graphics settings.
Weapons cannot be "leveled up" in TF2
You can't, but you can delete all your Achievements and start over.
Get achievements...
The dead ringer in tf2 can be obtained by a timed drop, or by completing Spy Achievements
No, since your achievements are stored inside Steam Cloud, otherwise people could just edit the relevant file(s) to get all the achievements.
The Bonk atomic punch in tf2 can be obtained by a timed drop, or by completing Scout Achievements
You can get the gunslinger by completing Engineer-related achievements, or from a timed drop.
you can receive them via a random drop about every 30min or get them via achievements. you can also trade them with other players
you can find the transcripts from the "Meet The..." series on the tf2 wiki.
Yes. TF2 is a GREAT game, and I recommend you "buy" it. TF2 is now free to Play.
No, TF2 is not playable on a phone
TF2 is free-to-play
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.