Bechorot 12 - What is Not Good for Redeeming a Firstborn Donkey

One cannot use the following to redeem a firstborn donkey: a calf, a wild animal, a slaughtered animal - even a slaughtered sheep, a sick animal - terefah , a hybrid - even an offspring of a male goat and a female sheep, or a koy - an offspring of a deer and a goat. Rabbi Eliezer allows redemption with a hybrid, because both a goat and a sheep separately can be used.

Can we redeem a firstborn donkey with a live fetus found in a womb of a slaughtered sheep? Is it a live sheep, good for a redemption, or, since it does not require proper slaughter, it is considered as meat already slaughtered, not valid for redemption? Can one use a mutant - an animal that is similar to a different species? Is it close enough to hybrid, which is forbidden? Can one use a disqualified sacrifice? Since the sanctity of a donkey cannot possibly go over to the sacrifice, the redemption is not possible, or does this sanctity just fly away? Can one use the produce of the seventh (Shemittah) year for redemption? Is it closer to prohibited commerce or to permitted food?

Art: William Snr Luker - Deer In The New Forest