I need an app that tells about file & folder sizes, like what is the biggest file and/or folder on my hard disk, sort this detail from biggest file and/or folder to the smallest & vice versa, also able to tell me about this detail based on the folder that I have chosen.
you can easily do this at the command line by executing the following at the root (/),
du -sk * | sort -nr
For directories only you can execute:
du -sk */
You could try Disk Inventory X.
Disk Inventory X is a disk usage utility for Mac OS X 10.3 (and later). It shows the sizes of files and folders in a special graphical way called "treemaps". If you've ever wondered where all your disk space has gone, Disk Inventory X will help you to answer this question.
I recommend DaisyDisk. Files and folders are visualized by a ring chart, makes it easy to identify which file/folder takes the most space in the hard disk.
The trial version has no limit on time, just a nagging screen when you launch the app.
You might be interested in GrandPerspective.
There is also OmniDiskSweeper.
There are two GUI applications for Mac that help visually identify what's taking up disk space: Disk Inventory X and GrandPerspective. If you've ever used KDirStat or WinDirStat then you should be comfortable with it, but even if not it's fairly self-explanatory when you run it.
You can also search by file size in Finder.
My favorite is Space Radar (Electron-based, MIT license).