For ectobiology you attempt to appearify something/someone in the past but they can’t teleport to you or they’d break their timeline so what appears before you is a bunch of goop basically has their dna/genetic makeup.

John did this for Nanna, Mom Lalonde, Bro Strider, and Grandpa Harley.  Half of this goop was used to make clones of those people which would later be sent into the past to become those people.  And the other half of the goop was used to make the kids.  Nanna and Grandpa Harley’s goop was mixed together to create baby John and Jade. While Bro’s and Mom Lalonde’s was mixed together to make Rose and Dave.

Karkat’s was a bit more complicated because trolls.

I tend to overwhelm people when I talk about Homestuck one-on-one so I usually keep it inside.

no

No, they already made the Genesis Tadpole, they just need to go get it from Echidna.

She made it

Not in story (not counting Mini-strife)  but in official Homestuck merch, yes.

Are you asking about Homestuck or actual Homosuck?

It’s canon.  Every player gets one when they get high enough on their echeladder.  The necklace allows them to summon their sprite anywhere.  It’s customary to give the pendant back to the sprite when the player doesn’t need them anymore which is why Davesprite has his.

It has not been featured in comic.

Bro is from the Pre-scratch universe and Drik is from the Post-scratch universe