Server concept understanding

I have hard time understand how does moralis implement server idea.

  1. Each time when you create a server that you have to select a chain to begin with, which chain should you select (as I can see there are both Layer 1 and layer 2 level blockchain, for example polygon is L2 chain on Ethereum L1 chain, does this mean if I create server on polygon chain it will also automatically works on Ethereum main chain?)

  2. once a chain is selected, does this mean the server is only connected to the that specific chain and can only work with that chain forever?

  3. Dapp and blockchain are designed to be decentralized, which the backend of Dapp is smart contract that eventually should run locally at each node’s EVM. But whole moralis feels VERY WEB2. Does this mean we as developer build Dapp under web2 structure for web3? How doe moralis eventually translate all of this and make the Dapps run decentralized? and we are not even coding with solidity but JS, we know on Ethereum we can not code with JS. This whole server thing feels very odd to me conceptually.

  4. Can you please try your best ability to explain the logics and implementation behind moralis server? how exactly does server connect to each different blockchain and how exactly it magically works with Dapps