Is there is any difference between 'upanishad embedded in veda' and 'upanishad attached to Veda'?
Please give any example.
Those terms are superfluous and artificial. Upanishads were never separate texts in ancient or medieval times. They were just contiguous chapters in a Veda Samhita, Brahmana or Aranyaka.
Even in the commentaries of Sayanacharya (14th century), we don't find references saying "this Upanishad" or "that Upanishad". The reference is to a Vedic text, such as follows:
In the commentary on Rig Veda 6.9.5, he references Ishavasya Upanishad as "Vajasaneyakam":
तथा च वाजसनेयकम् - अनेजदेकं मनसो जवीयः ...
So the classical Upanishads are all only chapters in Vedic texts, that were specially studied in the context of Vedanta. In modern times, it became popular to only study Upanishads removed from their parent texts, in isolation.
So there is no "attached" or "embedded".