psqlodbc && nested transaction

Hi,
I have got some problems about psqlodbc.
1. I have read documents about odbc(Microsoft) https://docs.microsoft.com/zh-cn/cpp/data/odbc/transaction-performing-a-transaction-in-a-recordset-odbc?view=vs-2017
It mentions that " Only one level of transactions is supported; you cannot nest transactions. " What about postgresodbc ???
2. I have tried the test directory and i also found some file that used transactions, such as the document i uploaded( /test/cursor-block-delete-test.c).
in this file i can only see the SQLEndTran(), and i am wandering whether there is something methods that i can use to create subtransaction like what i do in the postgres.
3. In the file , i can only find the method(SQLExecDirect()) that can handle the tranaction. Is there anyother functions that i can use to handle the transaction?

I am a beginner of the pogramming, and my English is very poor. Thank you very much for occupying your time reading this mail. And your any advice will help me a lot!
Thanks a lot!