Praise be to Allah, and may peace and blessings be upon the Messenger of Allah. To proceed:
It is authentically established that Allah تعالى has a Greatest Name by which, when He is called, He responds, and when He is asked, He gives. The scholars have differed concerning its identification. Among the most famous opinions is that the Divine Name “Allah” is the Greatest Name, while another opinion identifies it as “Al-Hayy Al-Qayyum” (The Ever-Living, the Sustainer of all). Supplicating Allah by this Name does not mean that what is requested will necessarily be granted immediately or that extraordinary events will occur. Knowledge of it is also not restricted to the awliya', and it is permissible for a Muslim to ask Allah تعالى to open for him the way to knowing it.
Authentic hadiths establish that Allah تعالى has a Greatest Name, and that whoever calls upon Him by it, He answers his supplication, and whoever asks Him by it, He gives him.
Allah تعالى says:
“And to Allah belong the Most Beautiful Names, so call upon Him by them, and leave those who deviate concerning His Names. They will be recompensed for what they used to do.” [Al-A'raf: 180]
Scholars have stated that all of Allah’s Names are beautiful, and among them is the Greatest Name whose virtue is indicated by the revealed texts.
The scholars have differed regarding the identification of the Greatest Name of Allah. Al-Hafiz Ibn Hajar رحمه الله transmitted numerous opinions concerning this matter.
One of the most famous opinions is that “Allah” is the Greatest Name, because it is the comprehensive Name that encompasses Allah’s Most Beautiful Names and His exalted attributes.
Ibn al-Qayyim رحمه الله stated that the Name “Allah” indicates all the Most Beautiful Names and exalted attributes through the meanings of correspondence, inclusion, and implication.
Another opinion holds that the Greatest Name is “Al-Hayy Al-Qayyum”, an opinion chosen by Shaykh Ibn Uthaymeen رحمه الله, who stated that “Al-Hayy Al-Qayyum” is the Greatest Name of Allah by which, when He is called, He responds, and when He is asked, He gives.
Accordingly, the matter is a subject of scholarly disagreement, and it is not correct to claim that the scholars unanimously agreed upon one particular Name. Nevertheless, the view that “Allah” is the Greatest Name is among the most famous opinions, followed by the view identifying it as “Al-Hayy Al-Qayyum.”
The fact that Allah responds when called upon by the Greatest Name does not mean that whoever knows it becomes capable of causing extraordinary events, achieving impossible things, or necessarily receiving everything he asks for immediately.
Rather, this indicates the great significance of supplicating Allah through His Most Beautiful Names, and that supplicating Him by the Greatest Name is among the means of having one's supplication answered.
The answer to supplication does not necessarily mean receiving exactly what was requested immediately. The response may take different forms: Allah may grant His servant what he asked for, store up an equivalent reward for him in the Hereafter, or avert from him an amount of harm corresponding to his supplication.
Therefore, a Muslim should not link the acceptance of supplication exclusively to receiving the requested thing immediately. Allah's response to His servant may take another form that is better for him.
No. Knowledge of the Greatest Name of Allah is not restricted to the awliya' of Allah or to a particular group of righteous people.
The door of supplication is open to all believers. Every Muslim is commanded to ask his Lord, persist in supplication, have good expectations of Him, place his trust in Him, and take the means that contribute to the acceptance of supplication.
Allah may grant some of His servants knowledge and understanding that He does not grant to others, but it is not correct to say that knowledge of the Greatest Name is confined to a particular class that others cannot reach.
There is no harm in a Muslim asking Allah تعالى to grant him knowledge of His Greatest Name and to open for him the doors of knowledge and supplication.
However, the servant should not become so preoccupied with this matter that he neglects the greater objective, which is worshipping Allah, calling upon Him, and drawing closer to Him.
Allah تعالى says:
“And to Allah belong the Most Beautiful Names, so call upon Him by them.” [Al-A'raf: 180]
And He سبحانه says:
“Say: Call upon Allah or call upon the Most Merciful; whichever you call upon, to Him belong the Most Beautiful Names.” [Al-Isra': 110]
Therefore, a Muslim should call upon his Lord by His Most Beautiful Names, choose from His Names those that correspond to his need, while maintaining sincerity, presence of heart, and persistence in supplication, and avoiding the causes that prevent its acceptance.
It is authentically established that Allah تعالى has a Greatest Name, and the scholars have differed concerning its identification. Among the most famous opinions is that it is “Allah,” while another opinion identifies it as “Al-Hayy Al-Qayyum.”
Supplicating Allah by it does not mean that a servant acquires the ability to cause extraordinary events or that what he requests will necessarily be fulfilled immediately. Rather, the answer to supplication occurs according to the good that Allah تعالى decrees for His servant.
Knowledge of the Greatest Name is likewise not restricted to the awliya'. A Muslim may ask Allah to grant him knowledge of it, while continuing to call upon Allah through all of His Most Beautiful Names, persistently supplicating Him, relying upon Him, and being content with what He decrees.
And Allah knows best.