Kali Hays,Technology reporterandRegan Morris and Peter Bowes,Los Angeles ReutersThe head of Instagram has defended his platform against claims it caused mental health damage to minors, arguing in a California court that even seemingly excessive use of social media does not equal an addiction.Adam Mosseri, who has led Instagram for eight years, testified in the landmark trial that began this week in Los Angeles, making him the first high-profile executive to appear. It is expected to last six wee...