Although you can enter a value in the text field in Indesign, this is not a default value, and is removed when you export. In Acrobat, you can set a default value by selecting Properties (of the field) > Options > Default Value [enter whatever you want as default].
If the text fields are named the same, the value entered in one field will be repeated in all.
Note in Indesign, duplicating a field will not retain the field name. You will need to change the name of each, and keep consistent.
Not sure about your comment regarding text fields becoming merged?
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