Questions

1. In the definition of stagnation conditions we imagine a fluid element moving with the flow is brought to rest adiabatically when we define T₀ and h₀ but is brought to rest isentropically when we define p₀ and r₀.  Similarly, In the definition of sonic conditions we imagine a fluid element moving with the flow is brought to M = 1 adiabatically when we define T* and h* and isentropically when we define p* and r*. Why do we make this distinction in the two definitions and demand isentropic deceleration / acceleration for two of the parameters but only adiabatic deceleration / acceleration for the other two?
2. How do the critical conditions (T*, p*, r*, etc.) differ for isentropic / adiabatic flows and flows with heat addition?