A matesprit is essentially a romantic partner whom you can reproduce with. A moirail is your soul mate but in a more platonic sense. They pacify you and function as a balance for you emotionally.

They were both created via ectobiology. The Draconian Dignitary created Bec and crockertier Jane created GCat. This is how all First Guardians are formed.

Separate sessions have separate moons. 

She didn’t, it was John who suggested that she refrain from dating him. Her not dating Dave allowed him and Karkat to become friends immediately instead of being at odds over Terezi.

The Warhammer of Zillyhoo was from a Problem Sleuth fan-requested game command.

Source

Submitted by==> zoidetrap

Yes

Terezi and Dave dated pre-retcon but they didn’t post-retcon.

Here’s her wiki page. 

Nepeta drew a diamond between them on her shipping wall here so they were most likely moirails.

Trolls hatch from eggs laid by the Mother Grub. Adult trolls fill filial buckets with their reproductive fluids and the Imperial Drones bring these fluids to the Mother Grub. She combines the fluids all into one incestuous slurry and lays thousands of eggs at once. They hatch and appear as small caterpillars with heads but later pupate into a humanoid.