Q1: The Summer Solstice is not usually the hottest day of the year because the Earth and oceans take time to warm up. Even though we get the longest daylight on this day, heat keeps building for several more weeks, so the hottest days usually come later.
Q2: On the Summer Solstice, the Sun rises very early and sets very late. This gives us the longest day of the year. However, the exact earliest sunrise and latest sunset may not happen on the same day because of the Earth's movement and tilt.
Q3: If I stood exactly on the Tropic of Cancer at noon during the Summer Solstice, my shadow could become very small or even disappear for a moment because the Sun would be directly overhead.