First of all, I'm not asking for evidence whether Professor Snape was a vampire, or if he was an Animagus, or if he could fly. I'm curious if he knew how to transfigure into a bat using any magical mean (drinking a potion, casting a spell, etc.).
Again, and to make it simple, my question is: Does Snape know how to transfigure in a bat?
The prior question: Can Snape fly without metamorphosis? is different from mine. I am not asking if Snape can fly.
I am bringing the bat transfiguration based on the possibility that Snape himself or Voldemort or Dumbledor or someone else taught him how to transfigure in a bat. Let us remember that in case that Voldemort taught Snape how to become an animagus, Snape was unregistered.
Regarding the transfiguration into a bat, there is a reference from J.K. Rowling in chapter one of Quidditch Through the Ages (2001), about a 'Human to Bat' spell, but according to Kennilworthy Whisp, this was one of the few ways wizards could fly unaided but, it was inconvenient because a bat lacked the memory required to remember important things.
No spell yet devised enables wizards to fly unaided in human form. Those few Animagi who transform into winged creatures may enjoy flight, but they are a rarity. The witch or wizard who finds him or herself Transfigured into a bat may take to the air, but, having a bat’s brain, they are sure to forget where they want to go the moment they take flight.
In other words, in the Harry Potter universe exist at least one spell to transfigure a human into a bat.
There are several references in Rowling's Harry Potter Volumes where it is said that Snape "looks like a bat" as follows:
In Volume 7 of Deathly Hallows, Chapter 30 'The Sacking of Severus Snape', Snape used his skills to escape from Hogwarts after his duel with Minerva McGonagall:
"No, he's not dead," said McGonagall bitterly. "Unlike Dumbledore, he was still carrying a wand...and he seems to have learned a few tricks from his master." With a tinge of horror, Harry saw in the distance a huge, batlike shape flying through the darkness toward the perimeter wall.
Harry Potter and the Half-Blood Prince, Chapter 9:
Neville's muttered Jelly-Legs Jinx without uttering a single word, a feat that would surely have earned her twenty points for Gryffindor from any reasonable teacher, thought Harry bitterly, but which Snape ignored. He swept between them as they practiced, looking just as much like an overgrown bat as ever,...
Whit the information above, I'm curious if there's a canonical answer to whether Snape knew of or created a potion or knew a spell or other art that could transform him into a bat.