Hi,
1. What makes difference in using Adapter type as SOAP 7.40 from SOAP 7.1
Fist of all you should to see only one adapter for SOAP in PI 7.4. There is no signification differences between the usage.
2. Is there any difference in using SOAP adapter as SOAP Axis
SOAP Axis gives you more functionality but you need to install the libraries in PI, AXIS has not all installed with the PI installation. SOAP AXIS is useful is you want to work with restful services, special attachments like MTOM etc, but for basic configuration it is easier to use (and it works at the beginning) is the SOAP adapter.
3. Currntly we are running User Authentication and Certificate Authentication in receiver SOAP Adapter(how SOAP Axis is useful)
With user authentication or certificates is easier to use SOAP adapter. As far as i know the Axis adapter hasn't any special to work with this,
In my opinion to work with Axis adapter is a really headache, i use it if there is not another available solution with the standard SOAP adapter.
Regards.