Each chapter of a paper doesn't have to start with an odd number of pages. When typesetting a paper, it is usually suggested that the beginning of each chapter should start with odd pages, which can make the page typesetting more neat and beautiful and more in line with academic norms. But this is not mandatory, and the specific requirements can be determined according to the requirements of the school or publishing house. If you don't know the specific requirements, you can consult your tutor or editor.