As we have python web application, I need to know how to get live streaming in my web application from Milestone Server.I trying REST API, Is that a right solution?If 'YES', what would be the basic requirements apart from VMS and API Gateway2021R2

The newly introduced Rest API does not include the ability to fetch video data.

The newly introduced Rest API is currently incorporating the functionality that before its introduction was available using the Configuration API.

For fetching live video data you need to use Image Server protocol. The sample TCPVideoViewer uses protocol methods and can be translated in to Python.

https://doc.developer.milestonesys.com/html/index.html?base=gettingstarted/intro_soap_protocols.html&tree=tree_3.html

https://doc.developer.milestonesys.com/html/index.html?base=reference/protocols/imageserver_index.html&tree=tree_3.html

https://doc.developer.milestonesys.com/html/index.html?base=samples/protocolsamples/tcpvideoviewer/readme.html&tree=tree_3.html

As you have a web application I am thinking that you will find using the Mobile SDK better and easier. Please have a look at

https://doc.developer.milestonesys.com/mipsdkmobile/