Peace
FIRST OFF: Quran was the 2nd Book that was sent DIRECTLY to the 2nd Messenger Prophet – the Quranic Seal of the Prophets, just like the 1st Messenger-Prophet Moses but the only difference is that Moses was not able to see ALLAH directly but the Quranic Seal of the Prophets did! For this, please read Quran Chapter 53:01-20.
Further, ALLAH says in the Quran thru HIS Prophet
And not is for a MALE HUMAN BEING that ALLAH should speak to him except by revelation or from behind a partition or that He sends a messenger to reveal, by His permission, what He wills. Indeed, He is Most High and Wise.
From the above verse, ALLAH spoke to a male Human Being in a form of
A. Direct Revelation
B. Thru a Veil
C. Thru a Messenger - in this case it the Spiri Angel Messengers JIbril or Mikaal or both!
In the case of A, this Quran, Chapter 53 confirms that the revelation was directly reveal to the Quranic Seal of the Prophets!
In the case of B, the Prophets Joseph, Moses and his mother was spoken to "indirectly" in a veil without any 3rd party!
In the case of C, the Prophets Abraham, Lut, Esa and his mother - Mary, were spoken thru a 3rd Party - the Spirit Angel Messengers!
The use of the singular 1st Person
1 - God speaks in the singular 1st Person (I) to assert HIS absolute Oneness. This is in the Present Mode with respect to time when HE spoke directly to the Messenger-Prophet Musa and the Quranic Seal of the Prophets Ministries respectively! The following are examples:
Inform My servants that I am the Ghafoor (Forgiver), the Raheem (Merciful). 15:49
I am God, there is no god but Me, therefore you shall worship Me and observe the Salat to commemorate Me. 20:14
This is Me, God, Lord of the worlds. 28:30
Such verses relate directly to the Oneness of God, as a result we will not find any verses which speak of the Oneness of God or of worshipping God alone that employ the plural pronoun.
2 - We also note that verses which speak of God’s attributes and God’s beautiful names are always phrased in the singular 3rd Person. In this case these verses were spoken by the Quranic Seal of the Prophets which he was conveying to the other Messengers of his ministry!
God bears witness that there is no god but HE. 3:18
God will suffice you against them; HE is the Samee (Hearer), the Aleem (Knowledgeable). 2:137
HE is Qahir (Supreme) over His servants. HE is the Hakeem (Wise), the Khabeer (All-Aware). 6:18
To God belongs the kingship of the heavens and the earth, and what is in them; HE is Qadeer (Capable) of all things. 5:120
This is a proclamation for the people, and with which they are warned, and for them to know that HE is but Wahid (One) god, and for those who possess intelligence to take heed. 14:52
3. The following Quranic words speak of God’s greatness and how it can never be comprehended by the human being.
They can never fathom the greatness of God. 39: 67
4 - The plural is also used in the Quran NOT because of Royal sense, but since the message was conveyed to his Majesty the Seal of the Prophets directly and he in turn conveyed the message to his disciples – the Messengers of his Ministry and further these verses are all in the PAST & PRESENT with respect to the Ministry of the Quranic Seal of the Prophets!
We have sent messengers before you to their people. They came to them with clear proofs. Subsequently, We inflicted retribution on those who committed crimes and it was incumbent on Us to grant victory to the believers. 30:47
In 30:47 we read of three acts executed by God:
a- Messengers sent by God to guide the people from before
b- The punishment God inflicts on the criminals of those yesteryear
c- The victory granted by God to the believers of yesteryear
The three acts mentioned are not acts which take place during the Ministry of the Seal of the Prophets but in the Past, but they are all acts that are executed by a Supreme God to His servants. The plural here denotes the message of conveyance by the Quranic Seal of the Prophets! This implies to your question where the plural were used.
When Our command was issued, We saved Shu`aib and those who believed with him by mercy from Us. 11:94
A command issued by God in the PAST, thus the word ‘We’ and 'Us" is once again appropriate to denote the message of conveyance! The use of the plural is employed in the same manner in 11:40, 11:58,11:66 and those verse you mentioned!
In the Present - with respect to the Quranic Seal of the Prophets Ministry, read Quran 28:44 to 46
5. In 16:40 we witness the use of the plural to denote God’s supreme majestic power and authority whenever God wishes for anything to come into existence: In this case it applies to the two Messenger Prophets – Moses and the Quranic Seal of the Prophets as they were acting on behalf of God HIMSELF!
Our word to anything when We will it, is to say to it, "Be" and it is. 16:40
Hope this help.