In summery this is what happened and what did so far, it's not as long as it looks, so please bare with me.
I had this 1 year old WD my passport external hard disk (1TB) which recently started showing bad sector related problems.i thought of backing up the files but, it was nearly full and I didn't had 900GB+ space in my pc so I thought of buying a new internal HD but before I could do that, my passport just died, I was forced to format the drive so that windows can detect it.
try 01: attempted to recover files using recuva (deep scan),scan was manually stopped after 3 days only 25% scan was complete recovered around 60 GB files
try 02: again attempted to recover files using recuva for a day again scan stayed at 25% manually stopped
try 03: reported here while attempting in recuva,suggestion were considered still no luck none of the software gone as far as recuva
try 05: did sum research,then stumbled upon this great software called R-studio (premium),started using it I recommend this since it has scan pause and resume mechanism.
try 06: after 3-4 hours scan stopped at 25% and stayed there for 2 more hours until manually stopped.
try 07: thanks to R-studio log, I was finally able to find the problem it was CRC error causing both recuva and R-studio to halt at 25% log said data error (cyclic redundancy check (23).
try 08: Googled around, which brought me here again. somebody suggested making an image file or clone of the hard drive with error and and then applying recovery methods on that image.
try 09: again R-studio was best choice as I found in one of the posts here,image file copying gone smoothly till 238 GB done again same error came up and copying process presumably halted at around 25%(238 GB) resulted in manual stop.
try 10: ran chkdsk through cmd no error found.
so now I'm at a bit of cross road here,so my choices are,
choice 1: to find a best tool for diagnosis and fix my external hard drive, which actually fix the trouble unlike chckdsk,after I should attempt to make a clone of the entire drive and then run a scan using R-studio.
choice 2: to find a best cloning tool which makes .img file even from the CRC error infested drive and then ruining the scan using R-studio
choice 3: I should abandon this troubleshooting procedure and opt for a new one.
in all the three cases I need suggestions, tips etc. and please don't say I won't able to recover and should throw the HDD as I already mentioned I was able to salvage some of files.