The easiest way to modulate from G to F major is by modulating down to C major on the way. In that way you are moving down the circle of fourths/fifths.
The way you would modulate from D major to Bb major would be passing through a D minor chord then modulating to G minor to get to Bb major.
The corresponding minor key to G Major is e minor. The key signature will be the same, one sharp: F#.
There are five major seconds which occur in the key of F major - the first major second is between F and G, then between G and A, then between B-flat and C, then between C and D and finally between D and E. I hope this answers your question.
E A major second is equivalent to a whole note, or two semitones, and two semitones down from G-flat (which is enharmonically equivalent to F-sharp) is E, although it might be written as F-flat depending on the key signature. F-flat, E to G-flat would be a diminished 3rd, not a major second..
The relative major key of Gb minor is Bbb (double-flat). However to make life easier, one could just say the minor key is F# minor and then the relative major would be A.
The easiest way to modulate from G to F major is by modulating down to C major on the way. In that way you are moving down the circle of fourths/fifths.
In a mjor key, Do will be the name of each Key. In F major, Do will be on F. In G Major, Do will be on G. In Bb Major, Do will be on Bb. In C major, Do will be on C.
The key of G Major has one sharp: F#
The notes in the key of G major are: G, A, B, C, D, E and F#.
The key of G Major has one sharp: F#
The answer to this question is not always simple, however if you want a definite answer, look at the tips below: If you wanted to end on a perfect cadence, you should modulate to a G major chord and then move down to the tonic chord (C major). If you wanted to end on a plagal cadence, you would modulate up a fourth to a F major chord and then resolve on a C major chord. If you wanted to end on am imperfect cadence you simply modulate to the dominant chord (in this case G major) and end there. Finally, if you wanted to end on an interrupted cadence you modulate from the tonic chord (C major) to the relative minor, an A minor chord. So in most cases a song which began in C major should end in the tonic key (C major), however a song in C major can end in G major (an imperfect cadence) or in A minor (an interrupted cadence). Hope this helps.
F#, C#, and G#.
In B flat major the F is a natural F. In G major the F is F sharp unless you are told otherwise.
G Major has just 1 sharp and it is F#
There are five key signatures with G sharp, they are: A major/F♯ minor (3 sharps) E major/ C♯ minor (4 sharps) B major/G♯ minor (5 sharps) F♯ major/D♯ minor (6 sharps) C♯ major/A♯ minor (7 sharps)
Play in the key of C major. The only notes you play are A,B,C,D,E,F and G. If the tune was G,F#,G,A,G then that would probably be in the key of G as it ends on G and it has F#. Because G is a major 5th above C, move all the notes down a major 5th and you get the tune C,B,C,D,C which is in the key of C.
You would be either in the key of F or D minor. Impossible to say which one without knowing the chord progression or the melody; does the Dm or the F feel more like "home"? You could modulate to any key you like, but you're be more likely to modulate to a "close" key. Since F or D minor have one flat, the close keys would be those with two flats (Bb or G minor) or no flats (C or A minor). Most likely, you'd go to the dominant key, which would be C or A minor (depending on whether your tonic key was F or D minor).