Hi,

For your previous questions on the same, there is some solution provided and seems the answer is marked as resolved: https://www.odoo.com/forum/help-1/question/project-and-task-duplication-146234

if you are not looking to use the copy function, you can use create methods and create the record in the corresponding model.

Add a button:

<button type="object" name="copy_pro" string="copy button"/>

Then  in Python:

@api.multi
def copy_pro(self):
    for rec in self:
        # add all the necessary fields to pro_vals dict
        pro_vals = {
            'name': rec.name
        }
        new_pro = self.env['project.project'].create(pro_vals)
        # search tasks of this project
        task_rec = self.env['project.task'].search([('project_id', '=', rec.id)])
        for task in task_rec:
            # add all the necessary fields to task_vals dict
            task_vals = {
                'project_id': new_pro.id
            }
            new_task = self.env['project.task'].create(task_vals)

Thanks