Does Unity simulate a specific platform when rendering the game (play button)?

Let’s say you are making a game for the PS3 using Unity. The ps3 has 256 MB of ram. When you run the game pressing the play button would Unity limit the game to 256mb of ram or the cpu clock and sort of simulate the ps3?

No, play mode in the editor does not attempt to emulate the target platform.

Playmode is defined as #Unity_Editor. You can test what platform the game is currently running in with:

#if UNITY_EDITOR
		Debug.Log ("Player Controls: Running in Editor");
#elif  UNITY_STANDALONE || UNITY_WEBPLAYER
		Debug.Log("Player Controls: Running on PC");
#elif UNITY_IOS || UNITY_ANDROID || UNITY_WP8 || UNITY_IPHONE
	        Debug.Log("Player Controls: Running on Mobile");
#endif