Answer to Question 1
There are several possibilities here, described in Section 13.4. E.g., GAIA will use space-based interferometry to measure the miniscule movements of stars as they are tugged by planets orbiting around them. TESS will use the same strategy as Kepler but cover the whole sky. CHEOPS will measure the properties of known extrasolar planets.
Answer to Question 2
A helium flash is a runaway condition caused by a core that collapses to a degenerate state before helium fusion can begin. As a result, the core cannot respond to the radiation produced by helium fusion and the fusion rate goes unchecked.