Is it possible to use an 8 pin accessory on an iphone 4? A relative just bought a biofeedback accessory for an iphone 5/6 and was wondering if they could use it on one of my old iphones. She'd rather use an iphone without any data on it so people could use it without supervision, but the most recent one I have is a 4 (maybe a 4s, not sure).

I found this, but I'm worried it won't work. I know the best way is to just try it, and I probably will because it's cheap, but I'm interested in learning a bit about the differences between the two types of cables. Would a device built for the iphone 5/6 use a slightly different protocol? I see lots of adapters that allow new iphones to use old iphone accessories, but not the other way around. I assume a lot of that is just because there isn't a demand, but could there be a difference that results in only some accessories working in that direction?
You can read about the differences here

About the adapter You gave in the link, a reviewer wrote:


  If you're looking for an adapter to charge your 30 pin device* with a
  lightning cable, then you will not be disappointed. If you wishing to
  connect your 30 pin device* for sync to your computer*, then you will
  also not be disappointed for at least some 30 pin devices*.


Also many complain that the device they got does not work, so You should look for a more reliable one.

There is a post about this that the adapter stopped working after a new software version: https://discussions.apple.com/thread/5780896?start=15&amp;tstart=0

You should consider buying an USB to 30 pin or a more reliable 8 to 30 pin adapter like this (note that this only allows you to charge the phone. No data transfer)