How to generate signed_transaction, base_transaction?
Firstly, the signed transaction and the base_transaction will not be identical, the base_transaction will not have the signature in it. But yes they will look very similar apart from that.

What you are looking at is a hex-encoded transaction. You can decode it to see what information it contains using the decoderawtransaction API https://chainquery.com/bitcoin-api/decoderawtransaction