Why do tapered wings not stall at the root first?
I will try to make it simple without going into mathematical details.

Source
Here, λ = ctip/croot
The important factors controlling the lift in the Tapered wing.

The ctip being too small affects the Reynolds Number (as the distance travelled is very small). Assuming the constant speed, density and viscosity, Reynolds number only varies with the distance travelled (x) directly. As the tip distance is too small, Reynolds number is not much increased for the boundary  layer and therefore transition from laminar flow to turbulent can not happen. Also due to skin friction, the flow gets slow and becomes separated. The separation causes loss of Lift and thus Wing Tips stall first.

The sweepback effect makes the boundary layer tends to flow spanwise toward the tips and becomes separated near the leading edges of tip.




Increasing Span Efficiency Factor,e as it is higher for tapered wings, it produces more Cl.

There may be other factors too, that I might have missed. But these are the most prominent. You can refer to below image. The Red Line shows seperated flows.

Yes, wingroot has a higher effective AoA. It is easier to understand this way. For a given AoA, the wingtips suffer from downwash and vortices which decreases AoAeff and increases Induced AoA (AoAi). As the wingroots do not suffer from the vortices, their AoAeff is higher.

Figure 2 &amp; 3: FAA Pilot's Handbook of Aeronautical Knowledge
Figure 4: Introduction to Flight, Anderson