yes the reptiles develop in eggs
For one thing most reptiles are born from eggs, while most mammals give live birth. Second, reptiles are cold blooded, while mammals are warm blooded. Unlike mammals, baby reptiles are able to fend for themselves.
reptiles and amphibians have the most in common
they lay eggs
Mammals originated as land animals. Reptiles were the first vetebrates to have hard-shelled eggs and spend most of their time on land. Reptiles evolved into modern reptiles, mammals, and birds. Some mammals, since then, have moved partially or completely back into water.
Fishes, amphibians and reptiles are ectothermic while mammals and birds are endothermic.
There are a variety of features but one is the number of fenestrae in the skull. Mammals also have more differentiated teeth than reptiles. Furthermore, you can look at the gait. Mammals have a parasagittal stance, while most reptiles have a sprawled stance.
One of the main differences is independence ! Most baby mammals require sustenance from the mother in order to grow and develop (like puppies, kittens, baby pigs etc suckling from the mother animal) - Baby reptiles are completely independent from the moment they're hatched (or born) - and quickly go off in search of their first meal.
live babies
There are individual mammals that are bigger than individual reptiles, and there are individual reptiles that are bigger that individual mammals. However, the average size of all extant mammals is larger than the average size of all extant reptiles. Most reptiles are lizards and snakes, which are usually small. Only a few species of tortises, alligators, crocodiles, caimans, and very large snakes are big. Most mammals are bats, rodents, and shrews, which are usually small, but there are still hundreds of mammals that are big, including the biggest animal on the planet: the blue whale. There are more large mammals than there are large reptiles.
Mammals ? or do you mean like creatures, Insects, reptiles...
Most mammals produce food for their babies, not actually for themselves.
Most species of reptiles are carnivorous. As carnivores, they eat a variety of insects and larger reptiles like snakes eat other reptiles or small mammals.