Clause 1:
"So, you would hold that all current religious practices were religious from their first moment of use"
My response:
Your use of the absolute 'all' makes me inclined to say No.
Because I don't have enough information to say a categorical yes, therefore I will say i dont know.
Clause 2:
and are always religious even when those doing them are unaware of the religion?
My Response:
An action or practice taken from a religion is still a religious action, at least from the viewpoint of the others (in general) who are practicing that system of belief.
Ah! Now I think we can reach a point of agreement. You're talking about the perception of the action. So, for instance, if I genuflect or make a motion that looks like a genuflection (for whatever reason), someone in the Catholic church would likely recognize it as a genuflection, and would see it as that gesture. The same would go for moving my hand in the 4-point "sign of the cross" that is commonly used in the Catholic church. And in this, I think we can agree that those actions will be recognized as religious by those for whom they are religious.
If an athiest goes to a liberal Catholic Church, and decides (for giggles) to perform the act of receiving communion, he has performed a religious action in the view of the father/pastor, and the members of that church.
The atheist is able to be ignorant of the knowledge that the Catholic Faith states that he literally ate and drank the actual flesh and blood of Jesus Christ, and still actually do the act.
It was really just wine or grape juice and unleavened bread. But by eating and drinking it he performed a religious action.
In that context, I don't think it's even arguable. The atheist may not be participating in the religion, but he is consciously partaking in the rituals of it. He doesn't become a momentary Catholic, but he is sharing the ritual in a religious context. Some would feel uncomfortable doing so, some would not. In some faiths, this may be seen as inappropriate by those who practice the religion (as in the case of participating in Communion at a Catholic mass).
Now some religions require intentionality to be present, as well as a measure of informed consent to view the work/act/practice to be viable or valid.
Lets look at the sacrament of marriage.
From the bible-believer christian worldview,
God created this Institution with the creation of Eve for Adam to be able to fulfill the edict "be fruitful and reproduce".
He created them male and female. And God purposed this pairing to be the bedrock of the family unit.
In this worldview, all valid marriages are sacred/religious. And a male-male, or female wedding doesn't actually count as a valid marriage.
To the bible believer, who submits to the authority of scripture every valid marriage is sacred, and holy. Even marriages between atheists, or between Muslims, or a hindi man and woman.
To us, such a thing is holy. A Christian is not to have carnal knowledge a married person (to anyone other to whom they are directly married to), it is very close to blasphemy.
Eg.
Steve is married to Sarah
And Jimmy is either a batchlor or married to Janet.
Jimmy is a Christian. But...
Jimmy looks at Sarah every day at work.
Eventually,
Jimmy has become lustful and desires to have Sarah.
Sarah is married. Therefore, she is off limits.
Every marriage is sacred, even hers.
If Jimmy was a nonbeliever, he could do whatever he liked. Marriage is just paperwork and cohabitation.
But if Jimmy asked a bible savvy pastor for advice... he would be counseled to repent, or change his mind/thoughts about Sarah.
Because every valid marriage is sacred and holy.
That's an accurate statement of that worldview. One alternative worldview, of course, is that marriage is a civil contract (requiring a civil license, and which can be performed by a civil servant). Many of us get married outside any religious institution. There are parts of the wedding ceremony that we may observe that have a religious origin (and may be viewed as religious by those who participate in a religion that uses them), but we won't see any religion in them, ourselves.
As for the requirement of intent, I don't think this is something a religion can oversee. If someone doesn't intend to practice a religion, they cannot accidentally do so. Going back to the first part of this post, let me create a small thought experiment to clarify my point. Two people: Sam and Greg.
Sam was raised in a small, isolated community in a foreign land. In that community, centuries ago, raising your hand and offering your fist to someone was once a religious act. One of the gods they worshiped was the war god, "Fulna". Fulna granted strength to warriors, and was said to bless the bravest with the power to kill with one punch, and to the most selfless the ability to withstand any blow. A greeting among devout warriors was to punch each other (with moderate force) in the chest, each in turn. This was meant to show that each had been granted both powers. Over time, to shorten the ritual, this became a practice of a softer punch to the others' own fist. That belief system has long been abandoned (they all converted to another religion, perhaps Christianity), and the practice became a simple greeting.
Is Sam's fist bump still religious, even though they now (knowing the origin) see it as grounded in ancient mythology and superstition, rather than actually seeking the blessing of a god?
As for Greg, he grew up in the United States, and has only ever known the fist bump as a greeting. It never had religious significance in his culture. If he performs this greeting with Sam, is it religious? What about when not with Sam?
I can't see a reasonable argument for calling either man's fist bump "religious", though one of them certainly has religious origins. And if there were still adherents to the old religion in Sam's community, they would likely see it as religious, perhaps in both cases.