Yes
The notes of the A major scale are A B C# D E F# and G#. The notes in an A major triad are A C# and E.
G,b,d
C major triad : C - E - GG major triad : G - B - DD major triad : D - F# - AA major triad: A - C# - EE major triad : E - G# - BB major triad : B - D# - FC# major triad: C# - E# - G#F# major triad : F# - A# - C#Cb major triad : Cb - Eb - GGb major triad : Gb - Bb - DbDb major triad : Db - F - AbAb major triad : Ab - C - EbEb major triad : Eb - G - BbBb major triad : Bb - D - FF major triad : F - A - CA natural minor triad : A - C - EE natural minor triad : E - G - BB natural minor triad : B - D - F#F# natural minor triad : F# - A - C#C# natural minor triad : C# - E - G#A# natural minor triad : A# - C# - EG# natural minor triad : G# - B - D#D# natural minor triad : D# - F# - A#Eb natural minor triad : Eb - Gb - BbAb natural minor triad : Ab - C -EbBb natural minor triad : Bb - Db - FD natural minor triad : D - F - AG natural minor triad : G - Bb - DC natural minor triad : C - Eb - GF natural minor triad : F - Ab - C
The dominant is the 5th, which in the key of A-flat major is E-flat. Then an E-flat major triad contains the notes E-flat, G, and B-flat.
E Major triad consists of E, G# and B.
There's 3!!!! Lass!!!!!!!!333333333333333333333333333333333333333
Chords don't have "tonic notes". Scales do. The tonic note of the G major scale is G (in fact, the tonic note of the X major/minor scale will always be X). Chords do have roots, but that's equally boring: the root of the G major chord is G.
The E-major triad is composed of an E, a G#, and a B. To make this chord minor, flat the G#.
C,e,g
No, the dominant triad is not always major. In a major key, the dominant triad is major (V chord), but in a minor key, the dominant triad is typically major (V) unless a harmonic minor scale is used, in which case it would be a major triad with a raised seventh (V7).
The note G would complete the major triad C - E - G.