IndiaQues. On Nokia lumia 520 - How to cancel vibration on back key and change the ringtone using memory card
ANS. No Doubt smartphones are integral part of our life considering the utilities & services they offer but on a number of occasions these features become a headache as we struggle hard to disable them but hardly find any solution as some of them are OEM specific but then here at Techtantrik we try to solve the problem in every way we can.
As per our commitment we tried solving your issue too but sadly there is no such feature to disable the key press feedback for some specific Lumia devices & we regret in saying that your Lumia 520 is also in that list. Though you may receive such feature in future updates but as of now there is no option available.
Moving on to your second query then i would like to say that there are a number for ways to change ringtone but that too with a twist as windows phone doesn't allow you to pick ringtones from sdcard however you can add the ringtone you want to the ringtones folder in Phone memory & then the new ringtone will automatically populate to your ringtones list which you can set & enjoy while receiving a call.
We really regret as we couldn't provide you a optimized solution to your problem but thing is these problems are related to OEM/hardware manufacturers which can only be solved by firmware updates. Though we gave you a alternative about the ringtone problem, hope that will help for the rest you can ask in comments.