Which animal is distinct in terms of embryonic development among mammals?

Which of the following phyla is not included in invertebrates?

Which one of the following characters is not typical of the class $Mammalia$?

The following statements regarding mammals are correct except:

Given below are statements $X, Y,$ and $Z$ regarding the duck-billed platypus. Select the correct option based on these statements.
$X =$ It is an oviparous animal.
$Y =$ It has a four-chambered heart and the aortic arch curves to the right.
$Z =$ It is a mammal.

Choose the correct option for the following statements:
$(i)$ Animals that maintain a constant body temperature are called $cold-blooded$ / $warm-blooded$ animals.
$(ii)$ Mammals are $viviparous$ / $oviparous$ animals.