I disagree with the first statement, kids like songs no matter their age. Teachers just need to find and use the ones they prefer according to their age.
I agree with this second statement, it is important to have and maintain a routine in class and once our students know them well, we can change the order if we consider it necessary.
I also agree with the third statement, during our lesson plan we can come up with extra activities for our fast finishers, but, as an option these students are useful to help other students that can't go as faster as them.