The dominant note is the 5th note in the scale. In the B Major scale, F is the dominant note.
The subdominant in a scale is the 4th, which in the key of B-flat major is E-flat.
b flat, c, d, e flat, f, g, a, b flat
G-flat major scale has the most with 6 flats: b-flat, e-flat, a-flat, d-flat, g-flat, and c-flat.Of course, one could argue that other scales have more flats (such as C-flat major, F-flat major, B-double-flat major, etc), but these scales are typically notated as their enharmonic equivalent (e.g. A major instead of B-double-flat major).
B flat major, with keys B flat and E flat
The dominant note is the 5th note in the scale. In the B Major scale, F is the dominant note.
The subdominant in a scale is the 4th, which in the key of B-flat major is E-flat.
The dominant is the 5th tone in the scale. In a D Major scale, the dominant is A.
The dominant of B is F#.
The mediant of B flat major is D.
The dominant of B is F#.
B-flat
Eb Major
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.
A-flat Major scale
The tonic of E flat major is E flat. Its dominant is B flat and its subdominant is A flat.
Your question doesn't make much sense. But for any scale, "do" would be the first note of the scale, which is whatever the scale is called. But for a flat major, from what it sounds like you're asking, the note would be a flat. Ex: In B flat major, "Do" is b flat.