List of every RFC or draft implemented/supported can be found in release notes for your particular release. Check main site for latest release notes.
User guide should resolve all your problems with BGP configuration.
Segment routing for BGP does not require any special configuration. If you have linkstate extension configured (which you have by default), BGP-SR is configured and supported implicitly. If you want to test it, insert routes with BGP-SR tlvs to ODL or command the router to do so.
BGP Flow specification does not require any user configuration. It is configured in ODL out-of-the-box, meaning ODL will send flowspec capability by default. If you want to test it, insert flowspec routes to ODL or command the router to do so.
Here you can find a guide on how to configure TCP-MD5 in BGP.
There are two RESTCONF pages that will show you learned BGP topology. You can learn about how to access them in this guide.
First, you need to configure special type of BGP peer - an application peer. Here is how you do it. Then you need to insert the routes, using this input as an example.
Currently ODL BGP has two BGP extensions implemented, linkstate and flowspec, so if you want to start creating your own, check the code for these two extensions as well as this tutorial .
Developer guide should be your start and mandatory reading if you want to know how BGP is implemented in detail.
Here is a list of statistics and how to view them as well as how to manipulate with the BGP session.
If you encounter something that does not match provided documentation, consult this troubleshooting site.