I would like to answer some of the questions:
“Why there is no difference between ventarl and dorsal parts, i.e. Nucleus Acumbens, VTA and dorsal striatum, SNc?”
In the DopAct framework the Valuation, Goal-directed and Habit systems are mapped on Ventral, Dorsomedial and Dorsolateral striatum respectively. It is assumed that that dopaminergic neurons in Valuation and Habit systems are mapped on VTA and SNc respectively, and dopaminergic neurons in the Goal-directed system may be in both these areas. In the full paper (https://elifesciences.org/articles/53262) the relationship of the model to experimental data from these regions are discussed.