creating a branch from Git commit ID within Github web UI

Here's how you do it.

First navigate to the commit in question, and then click on the <> button next to the commit in your history. This will show the web interface for browsing that particular commits snapshot of the repository.

Then, you see a small button with the commit id, just above the contents, like this:

Then, click the down arrow on this button to show the dropdown. It looks like this one allows you to browse different branches in the repository but you can actually create a new one. Simply type in the name of the new branch in the search field:

Then click on the "Create branch: ..." link at the bottom of this dropdown, and a new branch should be created.