Do the seven stages of development also apply to a religion, and does that take seven thousand years?

A religion does indeed develop in stages. But in the language of religion, numbers such as seven days or seven thousand years describe periods of development, not years by human counting.

In the language of religion, days, nights and years often describe periods in which a development takes place. They should not simply be converted into human years. The two verses above make this clear. In one place a day with God equals a thousand years, in another fifty thousand years. What is meant is not a calendar, but a period with a measure of its own.

Likewise, with the seven thousand years of religious history there is no sharp line between beginning and end. Only the decisive period in which the development is completed is named. The long earlier history that prepared it is not counted, because what matters is the outcome.

An image from science helps here. If the entire history of the earth is compressed into a single day of twenty-four hours, human beings appear only in the very last second. And yet everything before served that last second. It is the same here. There were human beings long before this period. The seven thousand years do not mean that humanity is only that old or that it ends afterwards.

After the peak, a long period of decline may follow. It can even last much longer than the rise itself. So a religion does pass through stages of growth and completion. But how long each stage lasts is not measured in our years.