By means of this spell, you use an animal to deliver a message. Choose a Tiny beast you can see within range, such as a squirrel, a blue jay, or a bat. You specify a location, which you must have visited, and a recipient who matches a general description, such as "a man or woman dressed in the uniform of the town guard" or "a red-haired dwarf wearing a pointed hat." You also speak a message of up to twenty-five words. The target beast travels for the duration of the spell toward the specified location, covering about 50 miles per 24 hours for a flying messenger, or 25 miles for other animals.
When the messenger arrives, it delivers your message to the creature that you described, replicating the sound of your voice. The messenger speaks only to a creature matching the description you gave. If the messenger doesn't reach its destination before the spell ends, the message is lost, and the beast makes its way back to where you cast this spell.
At Higher Levels. If you cast this spell using a spell slot of 3rd level or higher, the duration of the spell increases by 48 hours for each slot level above 2nd.
* - (a morsel of food)
Only issue with that is Vampires are shapechangers. Polymorph doesn't work on shapechangers. "This spell transforms a creature that you can see within range into a new form. An unwilling creature must make a Wisdom saving throw to avoid the effect. The spell has no effect on a shapechanger or a creature with 0 hit points."
Different classes have the spell. Only Bard has both. Sending being better doesn't help the druid that can't cast it.
It doesn't mention if the Animal can share the message multiple times. I could see instances where that might help. "There's an army coming from the east, flee!" Spreading your message to multiple people, instead of one, albeit, slower.
Rules for ritual casting just say that it has to be one of your known and prepared spells, basically if you have the ability to up-cast (including components) you can ritually up-cast
This is not true. The Player's Handbook's section on ritual casting specifically says that "the ritual version of a spell can’t be cast at a higher level."
In general, to upcast a spell you have to actually be using a spell slot.
This has another, although admittedly niche use:
The party has gotten lost in the forest/jungle/wherever.
Tell a nearby birdie "Go to <place we came from> and say "Hello" to the first townsguard you see"
The idea is not to actually deliver the message, it's to tell you definitively which direction you originally came from and therefore just go the opposite direction to where the bird went and you're on the path to your destination!