This group of mammals is known as monotremes. It includes the platypus, short-beaked echidna (both endemic to Australia) and the long-beaked echidna of New Guinea.
The only way in which platypuses are like reptiles is that they lay eggs.
Reptiles are born in eggs. It is part of what makes them reptiles.
lay eggs like all reptiles
via eggs like most reptiles
All reptiles lay eggs. Reptiles are animals that have scales, are cold-blooded and lay eggs, like turtles and snakes and lizards.
They did not carry their eggs. Dinosaurs kept their eggs in nests just like modern birds and reptiles.
Birds, reptiles and fish lay eggs (although not all fish do). The platypus also lays eggs (it resembles a bird but is actually a mammal). animals like birds, fishes and reptiles lay eggs. These animals are collectively called oviparous animals.
All reptiles and some mammals like platypus
Yes, they then lay eggs, like most reptiles
All reptiles lay eggs some are hard some are a strong plastic-like material.
Reptiles and birds have amniotic eggs, as well as the occasional mammal like the platypus and echidna.
How do Mammals reproduce? How do fish reproduce? How do Birds reproduce? Sex. Reptiles, like all of the other things I listed. Have sex.