question about keys need help

Since i cant seem to get an answer from Bodom I Was hoping somone else could help.
http://www.all-guitar-chords.com/lesson.php?id=3

so for the charts in this link (its about keys view it first)

1. So if I want to find the key of something all i have to do is use the above chart and match the chords/notes?
2. Say for example i play all the notes in the key of A not chords. Is that still the same key?
3. Just so I don't have to use this chart whats the best way to remember this (should I just memorize everything on the chart)?
4. so if i find the key say i' m in the key of G I can use any scale that starts with the key of G ?

1. ehh kinda. it may work some of the time but not all the time depending on the song

2. im not sure i understand? notes make up chords. chords are made up of notes... ur saying you use the notes in thhe key of a but dont play chords in the key of a?

3. take theory classes in your school. learn the circle of fiths, eventually u memorize it.

4. you can use any mode in the key of g. like e minor. or a dorian. b phrygian...and so on. however it all depends what chords you play, where your tonal center is and where the chord changes are.

Just needed clarification
1. I think i now what you are saying And that is that yes you can find any key of a song with the chart but sometimes artists add other chords or notes

4. Let me reword this. Say if i want to improvise in a song and i know the key of the song (lets say G) can i use any scale that is in the same key as G

You should really study the circle of fifths. I have a circle of fifths chart hanging on the wall in my guitar room and I use it often.

There is a lesson on the circle of fifths on this site in the lessons section but I have found it only scratches the surface.

I have learned a lot more about it since I wrote that lesson I really should update it a bit.

I think it would be a good place to start.

1. well somtimes artists go out of key. they go by what sounds good and stuff. most of the time you can figure it out.

4. yeah definatly lets say its a diatonic progression in g, 1 4 5, that would be g c d. then you can solo using the ionian, lydian and mixo. i feel if i explain it anyfurther you would be lost so ill leave it at that.