1) We are 'all' different because of our genome codes (DNA) are combined differently.

(Bacteria and micro-organism are mostly 'identical' replicates.)

2) This depends on 'reproduction' characteristics.

-- Bacteria reproduce by 'cell-devision'

-- Plants generally have male and female organs.

-- Ants, bees, wasps, lions, and many 'group animals', and have more females than males.

-- Some male fish turn into female after a certain age.

-- Among human, there are roughly equal number of males and females

(Even in cultures like in China and India where 'male children' are very much preferred.)

3) I do not 'know' enough facts about "types of chromosomes" to answer this question.