Yes, no reason to believe what?If you can't answer the question, who or what is God or at least have a stab, I really don't know what you are doing on this thread.
I've already answered that but for those with limited understanding, here goes again. I have no reason to believe and therefore don't believe in any of the myriad of gods which have been/are a part of human society. Get it?
If, as an example, I take the god of the old testament, I find he looks like a man, he is carnivorous, he is not omnipotent, he changes his mind, he spreads dung on people's faces, he even had a bear kill 42 children for calling a prophet, baldy. My take on this is that this god is no more than a human creation.
Your own response, I believe, was 'the Ultimate', which explains nothing of any substance. Indeed, if I follow your own description of 'ultimate'(
https://en.m.wikipedia.org/wiki/The_Ultimate) it leads me to the word 'absolute'(
https://en.m.wikipedia.org/wiki/Absolute_(philosophy) which simply says " In theology, the term is also used to designate the supreme being.". In other words we're back to square one and I'm none the wiser.
The question "What is it you believe / don't believe comes from Chomsky and he is as far from stupid as it gets.
You'd have to give me the exact source of your quotation for me to comment on this.
You did say you don't believe in God or gods ( however you construe them) because they are human constructs. Do you disbelieve all human constructs or do God or gods have a particular quality?
I suggest constructs are attempts at explaining various psychological or social phenomena in the absence of any objective means of substantiating them. As such they may well have beneficial or detrimental effects and may change as more evidential knowledge is gained. Whether they are true or not would depend on objective evidence supporting the construct. In the particular case of god(s) I have no reason to think otherwise than that they are the creative inventions of human beings.