A God that has always existed would be the only one who exists before anything else exists. God has special qualities, such as He is everywhere, knows you inside and out, knows the past, present, and future, is beyond time, can create out of nothing, has intelligence and emotions, and can do anything. There is only one explanation for all this, and that is that our reality is in the mind of the One God who is the Father of all things that exists in our reality. I'm sure that there are many different realities in the mind of One who has always been, and He is the Father of all of them. The Father is able to interact with each reality that He creates in His mind, through His Holy Spirit (which in Isaiah 63: 9-10 is referred to as the angel of His presence). The Holy Spirit is referred to as an angel because it can be sent by the Messenger (the Father) to indwell living beings and where His Holy Spirit is, the Father is. The Holy Spirit of the Father is a portal through which the Father can communicate His will and empower to perform it.
In our reality, He first formed a living being in it with his own intellect, heart, will, and spiritual body. The Father calls this being His Son and fills him with His Holy Spirit to such a degree that the Son becomes the visible image (in our reality) of the invisible God (the Father). Together, they create our reality (the Father through His right hand, the Son). The Father puts all creation under the Son's feet which makes the Son, Lord, Father, and God of all creation, but the Father is the Lord, Father, and God of all (including His Son).
Isaiah 43: 10 ... before me there was no God formed, neither shall there be after me.
Since there is a "before me", that would mean that time existed before the speaker. The speaker cannot be the Father, because the Father has always existed. It is the Son speaking.
Col 1: 15-16 Who is the image of the invisible God, the first born of all creation; For by him were all things created, that are in heaven, and that are in earth, visible and invisible, whether they be thrones, or dominions, or principalities, or powers - all things were created by him and for him; and he is before all things, and by him all things consist.
Here is the order of authority and Power in our reality: The Father, The Son, all others.
1 Cor 8: 5-6 For though there be that are called gods, whether in heaven or in earth (as there are gods many, and lords many), But to us there is but one God, the Father, of whom are all things, and we in Him; and one Lord Jesus Christ, by whom are all things, and we by him.