Answer to Question 1
Without radiation pressure to inflate it, the core contracts again and heats up, making the hydrogen burning shell expand as well.
Answer to Question 2
There are many answers to this: Mercury's spin-orbit coupling, Venus' runaway Greenhouse Effect, the Moon's synchronous rotation, the emergence of life on Earth and its absence on Mars, the Kirkwood gaps in the asteroid belt, and the rings and atmospheric appearance of the outer planets.