Who is the Most Merciful (Rahman) of Yamamah? And what is the difference between "Al-Rahman" (The Most Merciful) and "Al-Raheem" (The Compassionate)?

"Al-Rahman" is a name that signifies Allah Almighty's all-encompassing mercy for all His creation, while "Al-Rahim" denotes the specificity of mercy for believers. "Al-Rahman" is general for all types of mercy and is exclusive to Allah Almighty, whereas "Al-Rahim" is specific to believers, as stated in His saying: (And He was ever Merciful to the believers). It has been indicated that "Al-Rahman" is more intense in its exaggeration of mercy due to its generality in this world and the Hereafter for all His creation, and "Al-Rahim" is specific to believers. However, it is mentioned in supplication: "The Most Merciful of this world and the Hereafter, and their Merciful." The name "Al-Rahman" is exclusive to Allah; no one else has been named with it. As for "Rahman of Yamamah," it was a title Maslamah the Liar gave himself.