I want to migrate my production parachain from Kusama or Polkadot. How can I achieve this?
A migration from Kusama to Polkadot is possible. Done properly, the migration happens almost seamlessly; all the blocks, the state and the runtime are maintained. It is also possible to migrate from Polkadot to Kusama, or from any Polkadot-like relaychain to any other Polkadot-like relaychain, such as a from a custom Rococo relaychain to the public rococo relaychain. The whole process is unproblematic, as long as the entanglement via XCM with other parachains is not too strong yet, for example by having already exchanged tokens with another parachain, and as long as great care is taken when preparing and executing the migration.
A complete guide can be found at https://forum.polkadot.network/t/migrating-to-polkadot-a-complete-guide/2246