I am a blogger and just curious about how google index blogs in case they modified . so When an already published blogpost content getd edited or modified , does google re index it ?
The simple answer is "Yes".
Google will have a reindexing schedule based on how "important" it regards the content. For example Stack Exchange sites get reindexed very quickly as a search based on your title for this question will return this question already (hopefully).
So, at some point your blog will get reindexed.