There are no sharps in the key signature, but in the harmonic minor there is a G#.
F major and its relative harmonic minor, D minor, have only b flat.
If there are 4 flats in the key signature it means the key is either Ab Major or F minor.
No. Parallel key signatures share the same tonic, or starting note. Relative minor/major are the scales that share a key signature.
Each major key has a relative minor key and vice versa. For example a key signature with one sharp can refer to either the G major or the e minor keys. For major keys there is only one scale type. For minor keys there are 3: pure, harmonic, and melodic. In pure(natural) minor none of the scale degrees are altered. In harmonic minor the seventh scale degree is raised half a step. In melodic minor the seventh and the sixth scale degrees are raised half a step, ascending and returned to their pure minor descending.
There are no sharps in the key signature, but in the harmonic minor there is a G#.
Only "B flat" is the key signature, then "C sharp" is the accidental.
There is no key signature for D harmonic minor in particular - as the raised seventh is not part of the key signature. In all clefs, D minor has one flat and in all cases (since the raised seventh in this scale is C♯), to avoid confusion it is best to avoid having both a sharp and a flat in the same key signature.
The key signature for the harmonic minor scale changes depending on what key you are playing the scale in. For example, if you were to play a C harmonic minor you would play C minor (Bb, Eb, Ab) but sharp the seventh of the note (in this case, the Bb to B natural). This is just adding the leading tone into the scale. So, just to recap, play the minor version of the scale but add a sharped 7th. Now you have a harmonic minor.
F major and its relative harmonic minor, D minor, have only b flat.
There is not three notes in any scale or key, if you are asking about the accidentals, there is one flat (Bb) in the key signature plus an additional C sharp for the harmonic minor scale.
The harmonic minor scale, in relation to the natural minor scale, has a raised 7th scale degree. This happens with the use of accidentals rather than the key signature.
A minor has no key signature.
The key signature of E minor is F#.
D minor - more specifically, D harmonic minor (the version of the minor scale with a flat 6 and a sharp 7). However, you will never see a key signature with a B flat and a C sharp. The key signature will only contain B flat.
Both of them are diatonic scales. Major scale is written as per key signature. Harmonic minor scales have a raised 7th. The semitone leaps in these scales are different.
The corresponding minor key to G Major is e minor. The key signature will be the same, one sharp: F#.