It looks like you are asking how to stop a parachain from running.
If you have a permissioned parachain, then you as the controller of the parachain collators, just need to stop letting collators submit blocks, or stop submitting them yourself.
If you have a permissionless blockchain with its own governance and collator selection, then there is really nothing you can do since the community is in control of continuing the blockchain.
If you want to ritualistically halt your blockchain, you can consider having you or your community vote to upgrade the chain to a runtime upgrade which will brick your chain. A lot of chains have done this by accident, but you can of course do this easily on purpose.
Assuming your blockchain has halted, the only pieces of data left over from your chain (on the relay chain) is the latest Wasm runtime and the blockchain state root.
Polkadot does NOT hold all of your parachain data, only the state root. It is up to the collators, block indexers, and other full nodes to have the underlying data for your chain.
If you want to keep sensitive historical information about your chain around, someone will need to keep that data. It should not really matter if that data is centralized as you can always prove the data is correct by matching it to the state roots on Polkadot.
Assuming every copy of that data is deleted, there really is no easy way to recover that data or the history of your blockchain.