Question about "The Place I'll Return to Someday" music sheet

Question

There is a song I want to play with my 12 holes ocarina: "The Place I Will Return to Someday" (also known as "A Place to Call Home").

These are the music sheets:
Music sheet part 1
Music sheet part 2

Some questions about the music sheet (part 1):

1. Is the song key is C Major or A Minor? How to find out if it's C Major or A Minor? I saw there is big "A" letter above the time signature, does it mean the song is in A Minor?

2. There are two staffs, but it's not a grand staff as it seems. What does that two staffs mean? Is the song mean to be played by two instruments (duet)? If I want to play with my ocarina, is the top staff that I should play? so the bottom staff can be ignored?

3. If there are two note symbols stacked together, what does it mean? For example, look at the part with red square below:
   
   
   The high A note symbol and Rest symbol are stacked together, it seems contradictive to play and take a rest at same time. So how should I play that two note symbols?

4. Some note symbols has number on top, for example like the first note (D) symbol has number "1" above, the fifth note (A) has number "5" above, some others doesn't have number at all. So what does the number mean?

5. The four notes that has 1 2 3 1 number above seems doesn't sound good when played (see image below with red square), their existence just break the melody between high A and B note.
   
   
   Could you explain how to deal with those four notes?

Answer 1

"Is the song key is C Major or A Minor?"

This piece is in d dorian.

"How to find out if it's C Major or A Minor?"

There are no accidentals at the beginning of the staff which could apply to both C major or A minor. But apart from the diatonic scales, there are also modes, and this happens to be in d dorian mode.

The only way to really tell what key it is in is to listen, and try to discover what sounds as if it should be "the last note".

You can cheat a little though, and actually look at the last measure to see what chord you find there. In this case, it ends on a D major chord, indicating the tonal center would be on d. d dorian can be seen as a special case of the normal diatonic minor scale of d. This may seems strange that a piece which is in a kind of d minor scale ends on a d major chord, but this is not that strange. Sometimes that is called a "picardy third" (= major third in final tonic chord in an piece that is in a minor scale)

"I saw there is big "A" letter above the time signature, does it mean the song is in A Minor?"

No. This is a rehearsal mark - a label that identifies a particular section. You can use this as a recommendation to hook in when you're rehearsing the piece.

"There are two staffs, but it's not a grand staff as it seems. What does that two staffs mean?"

There is an accolade indicating the staffs form a unit. Most likely this score is originally for piano.

"If I want to play with my ocarina, is the top staff that I should play? so the bottom staff can be ignored?"

Yes, it seems the upper staff is the melody. The bottom staff is accompaniment. You wouldn't be able to play the bottom staff on a wind instrument (except, maybe bagpipes or organ) since it sports simultaneously sounding notes (chords).

"If there are two note symbols stacked together, what does it mean? For example, look at the part with red square below: "

It's two independent parts (voices) on one staff. The upper voice gets its beams up, the lower voice gets its beams down. You should pick one when playing the ocarina. I think it would make most sense to always pick the upper most voice when there are multiple parts in the measure.

If the voices are completely dependent, then you'll find multiple noteheads on the same beam. There's a lot of that in the lower staff.

"Some note symbols has number on top, for example like the first note (D) symbol has number "1" above, the fifth note (A) has number "5" above, some others doesn't have number at all. So what does the number mean?"

I believe this is fingering for piano.

"The four notes that has 1 2 3 1 number above seems doesn't sound good when played (see image below with red square), their existence just break the melody between high A and B note. "

That's because they are a second voice. The upper voice lets the a ring on while the lower voice plays this scale figure.

Answer 2

It seems you don't know much about sight reading beyond some basic things. I am not an expert either but I'll answer as well as I can:

1. The best way to find out if it's C major or A minor is to look for accidentals (sharp or flat signs) A minor scale not only has natural notes but also can have sharpened 6th and 7th notes (F#, G#) due to the special nature of minor scales (read up more about melodic and harmonic minor scales) If the piece has those notes then it's likely that it's in A minor, otherwise it's in C major (note that sometimes accidentals are brought in not according to the scale but for temporary special purposes of the composer)

2. Most likely it's a duet- to be played with two ocarinas. So you and your partner should decide who is going to play which part, if you want to solo yourself then pick the staff you like. I once arranged a duet for my solo playing purposes.

3. If two notes are stacked together then it's called double-stopping, meaning you play them at the same time. I understand your confusion about the bottom one being a rest but that too is logical. the upper note is a dotted note lasting 1 and a half beats while the rest is a 16th beat rest after which you start playing the other 16th note (C,D,E) while still sustaining the high A. let me be more specific- if we break down the dotted crotchet we have 6 16th notes. when you're playing the high A, the first 16th beat you only play A. but when you move on to the second 16th beat of the A note you start playing the C,D,E notes at the same time if you notice carefully- the notes above (dotted high A and 16th B,D notes make up two beats of the 2/4 time signature on their own while the bottom notes including the rest also make up 2 beats on their own. if played correctly and together as required they won't break the rhythm)

4. the numbers on top refer to the fingering they are instructing you to use particular finger patterns for playing the notes. you are free to use whatever fingers you like for non-numbered ones, but make sure to use same fingering for the notes specified until you are instructed otherwise. sometimes (in violin) the use 4 to mean using your fourth finger instead of the open string but if they want you to revert back they use a 0 on that note, meaning you can go back to the usual fingering.

5. the reason those notes don't sound well is most likely because you didn't understand how to play them to begin with (refer to answer no. 3)

Hope this helped :) I once heard the performance of Heian Zakura in my country where the female performer used a ocarina. It was lovely.