Is it possible to skip verification of blockchain data when using bitcoin core?
I just wanna save my bandwidth


Running a node in pruned mode will not save you bandwidth during the initial block download (sync), you still need to download all blocks and validate them, even if you don't store them longer term (pruning lowers disk space requirements). You can fine-tune your data upload limits in the bitcoin.conf file though. 

Most RPC calls will work with a pruned node, some will not though. From a quick search for some examples, see:

https://github.com/bitcoin/bitcoin/blob/v0.11.0/doc/release-notes.md#block-file-pruning

https://github.com/bitcoin/bitcoin/blob/v0.12.0/doc/release-notes.md#wallet-pruning