I wan to show the last posts in the sidebar on the index page.
I would like this to be done without the use of any addons, ie via template edits and using the xenforo helper functions to do so. Kindly please assist me on how to proceed.
I don't think you will be able to do it without using an add-on as you'll need to fetch the 'latest' posts from the database...
Or do you want something like fetch all the last post from each of the nodes from the main node list and display them in the sidebar block?
okay... so you have to port into XenForo_ViewPublic_Forum_List and extend renderHtml and get the list of recent posts from there. And then create a template modification to add a new sidebar block where the recent posts will be shown (you will need to stylize the look).