From openstreetmap, I want to download only the features that have specific change set comments (like #ABC). I already know how to download OSM data (using JOSM) and found this webpage shows filtered result only; no download option available (my required format) . It would be a great help for a newbie if anyone provides solution.
The trouble with your request is that it requires a lot of changeset data to be available and processed to find the ones matching your query. This is an unusual request (that would usually be done on a local copy of the data if needed), most live/public APIs focus on the current data of OSM not the changesets.
There is a service called "planet stream" that you can use to filter "diffs" and get the changeset/data desired. A diff is the data (and changesets) that have changed since the previous diff, in this case it's minutely diffs. You could build a system to collect the ones matching your query and record them over time.
- Blog post about Planet Stream, with example https://developmentseed.org/blog/2015/09/28/whats-trending-osm/
- Documentation of the Planet Stream API https://wiki.openstreetmap.org/wiki/Overpass_API/Augmented_Diffs
- Code of Planet Stream https://github.com/developmentseed/planet-stream