@cjrc97

Very good questions for the discussion.

i. The difference in velocity can be defined from continuity equation too. The streamline above is narrower and the streamline lower is wider. From the continuity principle;

div(ρ v) + dρ/dt = 0

Assuming in-compressible air; Av = constant.
When the streamline goes towards narrower region, velocity increases and towards wider, velocity decreases.
So, velocity increases at top and decreases at bottom.

ii. I guess, the lift produced by the symmetric airfoil is due to angle of attack. In zero angle of attack, the transit time will also be same.

iii. Regarding Bernoulli equation. we considered the flow before trailing edge as same stream line.
use bernoulli between top to before trailing edge and then bottom to before trailing edge which shows that the bernoulli can be taken up and bottom side.