The 24-year-old set a new Chinese record over 200m of 20.16sec in May to underline his electric form heading into the Games in Indonesia's Jakarta and Palembang.
Chand, affected by the same condition, hyperandrogenism, which has dogged the career of double Olympic champion Caster Semenya, fought and won a lengthy court battle to remain in the sport she loves.
The 28-year-old, running his first competitive marathon of the year, held off Swiss Tadesse Abraham by 1min 33sec, as Yassine Rachik took bronze for Italy.
The 33-year-old Frenchman joined the trio of German Harald Schmid and British pair Roger Black and Mo Farah as the sole athletes to have won five outdoor golds on the continental stage.
The Briton raced to 13.34sec in the opening 100m hurdles, just four-hundredths off her personal best, while the Belgian could only manage 13.69.
The 28-year-old Bett, the father of two-year-old twins, made his name at the World Athletics Championships in Beijing where he surprised the field by taking gold. He has since struggled to replicate that form.
Estonia's Magnus Kirt (89.75m) and Czech Republic's Jakub Vadlejch (89.02m) will be looking to challenge the German triumvirate.
Dagar, who won a bronze at the 2014 Asiad, tested positive for banned meldonium, the source close to the Athletics Federation of India (AFI) said.
Russian athletics federation President Dmitry Shlyakhtin said he had been hoping for better news.
The 33-year-old, who won Olympic gold in London and was the reigning world champion from 2011-2015, only managed third at the German championships last weekend.
The 25-year-old former world indoor 1500 champion arrived in the Netherlands as a refugee from Ethiopia 10 years ago.
The 21-year-old wins gold in 400m in which compatriot and 400m hurdles specialist Abderrahman Samba registers a personal best.
The 28-year-old from Kent had set a world mile best in the Anniversary Games Diamond League meeting in London a year ago.
The rapidly approaching introduction of testosterone rules could diminish Semenya's performances.
Noah Lyles races to a dominant victory in 200m.