You can exactly position a document object (e.g. Text Box) in a body of text, but as soon as you lock that document object in place, it is now immutable to content, and position change.
You won't see an Arrange tab, or its inherent Object Placement choices of Stay on Page, or Move with Text, until you select the object. To position and lock a document object into surrounding text, you must choose Stay on Page, and Text Wrap to Around. This will also reveal the lock/unlock option at the bottom of the Arrange panel.
No version of Pages provides frames. These are available in LibreOffice Writer, with substantial configuration options (e.g. multiple sections in a frame).