Multiple questions for noobs

[CaledoniaProject]

I'm new to graphql and I have several questions

1. Does graphql natively support MySQL/PG/SQLServer as backend? Or do I need a commercial solution?
2. When I search for "graphql docker" on google I found multiple vendors like Apollo or Hasura, what is their relationship with this repo?
3. If I don't use any relational database as backend, would graphql still work?