1) How can distinguish medium infantry from heavy infantry if both units for 8 figures?
The figures are distinctive, and you can see the troop-type by mousing over the unit. 1 figure = 60 men.
2) Would it be possible to combine 2 units of spearmen, increasing the depth of the 1 unit?
Not to combine 2 units, but the system would allow deep units of spearmen, if the period justified them. e.g. Thebans at Leuktra, and shallow units for the Athenian centre at Marathon.
3) Would it be possible to divide 1 unit of pikemen for 2 more thin units?
The system would allow such units, although there are none at present.
4) May be you can make it so Medium Cavalry (Light spears Cavalry and Camalry) will contain 3 figures, and Heavy Cavalry (Lance Cavalry, Cataphracts, Knight) will contain 4 figures?
Each figure represents 60 men, so there is no reason for lancers to have more figures than light spear cavalry. The figures are easy to tell apart anyway.
5) Is it possible to do a not linear placement of figures in the unit to display warbands, medium cavalry, camelry, skirmishers, mobs and undrilled heavy infantry?
Warbands and skirmishers have more untidy ranks than regular units.
6) With the loss of figures in the unit is decreases the power from each of the lost figures?
Yes