It is about the fingerings, and the reed... and...
Well, let me see if I can help. First, being the first possible A at the Alto, A1, the one with the octave key is A2 and first altissimo A is going to be A3. Is this A3 the one you call Super A?
G's are always hard to hit. G3 is as the next altissimo one is, G4, very hard to get but you eventually will.
Those notes demand fingerings even if you change your reed (not as for a new one, but from a brand to another one, for example). Some of the advices seem to be very useful, but not at all if you do not find help from a tunner.
Usually it is a low note, it tends to be a little lower than the middle, and you have to correct it and then many overtones and harmonics can be produced. This might be desired, but later on, when you learn to produce exactly the kind of note you want and then the effect you want.
Feel the note as it comes out and be very focused as it turns bad. That is the key for your embouchure to correct what is going on. Need patience and practice.
I personally use the fork fingering, but sometimes I use the side Bb key or whatever I feel fits.
Hope it helps,
JI