Pouneh

Hi everyone, 1.In Harmonization of a melody, do we use just the chords,that their notes exist in the respective Scale? I mean if our scale is G major, can we choose #F major or F minor? (Because they have the notes #C and #A) 2.If we want to use these chords, do we have to use them in the measures, which do not have the notes #C or #A? 3.what is the best chord to use? For example when we are again in G major, which one is better? -write a chord on 'g minor( Picardi)'? -write a chord on it´s next note (chromatic or diatonic) like #G major or A dim ? -write a chord on it´s relative minor (e minor) ? -write a chord on it´s Dominant? -non of them? actually I want to know if there is a preference to use the chords that they are creative and have a good voice? 4.we assume part of our melody consists of four notes (Mi dotted quarter note, Sol sharp quarter note, Si quarter note, Re sharp eight note), I want to write for these the E major chord (mi, #sol, si); is it ok or do I have to name my chord E major 7 (mi,#sol,si,#re)? how about the name of chord If the value of the notes (mi,#sol,si) was more than #re? Thank you in advance