Is there any way to know the RAM of an Android phone? I bought a Spice Stellar Jazz Mi-353. It tells me that it has 116MB of RAM, but it is supposed to be 256MB. Is there a way to check how much RAM my device physically has before deciding to get it replaced?
You can use an app that tells you what hardware your device has. 

There are a lot of apps like this and here you have some examples: Antutu, Android Hardware Info, Quadrant.