No I've explained how a necessary entity exists
No you haven't - and let's not forget you are actually talking about non-contingency not necessity (which we all accept exists and there are countless examples). You have completely failed to demonstrate that non-contingency exists.
... and why and in what way it is necessary.
Nope - complete fail on your part, compounded by the non-sense notion that consciousness and having 'volition and knows what it's doing' are key criteria for 'necessity (or rather non-contingency) when the evidence is clear that those attributes are contingent.
The alternative is for it to be a contingent thing and then we are entitled to question it's ultimacy.
Why is ultimacy relevant - except if you already have a pre-judged belief in a god that you are trying (badly) to shoe-horn some dodgy philosophical trope into trying to 'prove'. And you folks seem to have this all the wrong way around. Rather than fixate on the biggest, the most complex, the most sophisticated, the most ultimate (that way lies nonsense and infinite regress) the smart thinking is to focus on the simplest and most fundamental elements, as physicists tend to do.