Is it permissible to offer greetings of peace in various forms, such as: "Peace be upon you from a forgiving, merciful Lord" or "In the name of the Most Great Lord I begin my words... And upon His noble Prophet I send peace," or is the form of greeting restricted to "As-salamu alaykum wa rahmatullah"?

Multiple forms of greeting with "Salam" (peace) have been mentioned in the Quran and Sunnah. It is best to choose the most complete form to maximize reward, as "Salam" is an act of worship whose wording and manner should not be altered. "Salam" is the greeting of Adam and his descendants, even after entering Paradise, and "As-Salam" is one of Allah's names.

Regarding the forms mentioned in the question:

1. "Salam alaykum min Rabb Ghafoor Raheem" (Peace be upon you from a Forgiving, Merciful Lord): This is acceptable once or twice, but adopting it as a regular motto is disliked, as it deviates from the Sunnah. The intention behind it should be to supplicate for those being greeted, not to emulate Allah's saying in Surah Ya-Sin/55-58, for the meaning of that verse is that Allah Himself is greeting the people of Paradise.

2. "Bism Rabbil A'dham abd'ul Kalam, wa 'ala Nabiyyihi al-Kareem ursil as-Salam" (In the name of the Most Great Lord I begin my speech, and upon His Noble Prophet I send peace): This is not among the prescribed forms of greeting between people, nor is it a greeting upon them. The phrase "ursil as-Salam" (I send peace) is incorrect; the correct form is "As-Salamu 'ala Rasulillah" (Peace be upon the Messenger of Allah) or "Allahumma Salli wa Sallim 'ala Muhammad" (O Allah, send prayers and peace upon Muhammad). Limiting it to sending peace upon the Prophet without sending prayers upon him contradicts Allah's command in Surah Al-Ahzab/56; therefore, prayers and peace must be combined.