Not INSIDE your stomach but in front of your stomach, your belly, yes.
The leftover of your lunch ;D The stomach, as an organ, doesn't have a term to refer to the inside of it, as far as I know. In conversation, 'the inside of the stomach' will usually suffice in describing the inside of the stomach. Hardly detailed, but meh.
all of the food you ate goes inside the stomach inside your body
Mucous coats the stomach and protects the inside of it.
it keeps your food inside your stomach
Starfish turn their stomach inside out to capture food that is near them.
The stomach is hollow. There are no individual organs inside the stomach.
A baby NEVER sits inside your stomach
Inside your stomach you have an acid called "gastric acid".It turns the food that you eat from the esophagus into a liquid.
The inside is folded
Inside its body.