Im just getting used to bitcore.
Are you using bitcore or Bitcoin Core? If the latter, please do not refer to it as bitcore as Bitcore is an entirely separate software that is based on Bitcoin Core.
First task, add or import paper-wallet,
Take the decrypted private key from your paper wallet. Import it using
Second Task, Export bitcore wallet back to the same paper-wallet. Using the same address should be ok for these two tasks
That's not how Bitcoin or paper wallet work. You don't export Bitcoin and addresses are mapped to private keys (of which a paper wallet is just one private key) so you can't possible get a different address. You are importing private keys, not sending Bitcoin anywhere.
A? With bitcore wallet encrypted and with no password, should I be able to see the private keys in wallet.dat
Yes, the wallet.dat contains all of your private keys. They are not in a human readable format as that would be pointless.
or in recievingaddressexport.csv?
You should not see any private keys in that at all whatsoever.
How do I then delete all data in BC to make it fresh...
Go to the Bitcoin Core data directory and delete all of the files in there. If you delete your wallet.dat file, you will be deleting your private keys and they are not recoverable unless you have a backup.
B? Also, i mistakenly overwrote the first wallet.dat file with one of my public-address's in it but i had not imported a private key into it.
The wallet.dat contains the private key for that address, unless you had imported just the address. You don't need to import private keys for everything, Bitcoin Core will generate private keys and their corresponding addresses for you.