Default [Q] Phone not starting in download mode..

Hello,
I had flashed the CandyKat rom and now I want to get back to Stock and then G2V5.. But now I am stuck in a weird problem.. I am not able to switch on the phone in download mode.. I tried everything.. I pressed volume down only and inserted the data cable, again I tried holding both volume up n down.. still not working... Please help...
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Phones:

Nokia 1100 ---> Nokia 2310 --> Nokia 5130 & Lava Arc 04--> SE Xperia Arc --> Sony Xperia Z (Sold, Miss it ) --> Fiery Red Nokia Lumia 720(gifted to bro) --> Samsung Galaxy Y (For some days. thankfully ) --> New LG Optimus G Pro (AT&T E980 Unlocked 32 GB version)