Can I restore a blockchain.info wallet into a electrum wallet? If I have a blockchain.info wallet, I got the 12 words. Can I use these 12 words to restore into a new Electrum wallet? 

After that, will the blockchain wallet still operational? Say, can it still receive funds or spend fund? If fund is received/spent, will it appear in the new Electrum wallet?

On the other hand, if I send fund / receive fund in the new Electrum wallet, will those transaction appear in the blockchain.info wallet?
In Electrum:


Click File > New/Restore, enter a name and click Next.
Select Standard Wallet and then Next. 
Select I already have a seed and then Next.
Enter the 12 words seed you got from blockchain.info (from Settings > Security > Backup phrase.
Click the "Options" button and enable BIP39.
Accept the default derivation key and click Next.
In the next step, set a wallet password and enable encryption.


Now you have your wallet imported.


  if I send fund / receive fund in the new Electrum wallet, will those transaction appear in the blockchain.info wallet?


Yes, they will.