1) Why dance leaders are needed ?

Because , Srila Prabhupada said in Bg 3-21 purport “ in general always require a leader --” and without leaders nothing can be good and there will be no harmony. But ,when we dance in the guidance of leaders{ or expert in dance as recognized by seniors}
it looks nice and in harmony to please the Lord. In Caitanya Caritamrtam its said :
Vakreshvara Pandit was the chief dancer.--CC-Ant-4-11-50.

And Rupa Goswami said in Nectar of devotion :One should learn to dance before the deity.--NOD page 54 and 55.
That means the concept of dance leaders is coming from the time of Lord Chaitanya itself.

2) Who are dance leaders ?

Srila Prabhupada`s disciples, Sanniyasis , temple president ,senior devotees or their recognized devotees.

3) How many dance leaders ?

As much as singers or more.

4) What is right and what is wrong dance formation ?

At first devotees are allowed to demonstrate their formations to local leaders , get it recognized and finaly GBC can approved the authorized dance formations.

5) How to make permanent and easy solution for singing and dancing?

By performing regular , monthly or weekly singing and dancing-- training and leadership programme in all temples and centers;the temple
will become unique and it will bring transcendental atmosphere between devotees