Item Batch upload data file REST API Erroring out

Hi,

I am trying to use import map to load items using REST API. 1st step of creating import batch was successful, however when try to run upload a data file REST API getting below error.

Can someone help to answer below question

Question 1: Guide on REST API to load file to UCM server

Question 2: Upload File erroring out as below

Error details as below,

You must provide a value for at least one of these attributes: Batch Number,Batch ID.You must provide a value for the Import Map attribute.You must provide a value for the Data File Path attribute