Does AD2P bluetooth stereo headset work only with phones with AD2P support?

[drgre]

That's my doubt

I want to buy a bluetooth stereo headset, but I don't if this headset works with a phone like k750.

it will work, but only as basic (non A2DP) handsfree, you'll be able to take a calls, but not to listen to muzic... so, if you don't plan to change your phone to A2DP supporting soon, there is no point of buying stereo headset, you can get a "mono" one as well.

I have question, my k610i is support with Headset Bluetooth stereo made by Nokia?

sure it will, brand doesn't metter.