Just because of the sound. A questions has a large music at the final. Me amas = you love me ¿Me aaaamaaaaasssss? = Do you love me? ... more or less ;-)

They differ in the intonation of the sentence. It's hard to explain in words, you should listen and compare.

it means: me amas. It is very difficult to explain here because it depends on the accent. If you wanna talk with me and on Skype I can explain you this part.