Can you talk and text at the same time on iPhone 4?

You can talk and text on ANY iPhone, including Verizon's. (Actually on any phone). SMS (text) does not use cellular data; it uses the voice side channel. However, you cannot talk and iMessage at the same time on Verizon, or send MMS messages, because they use cellular data (unless you are connected to WiFi) and Verizon does not support simultaneous voice and data.

That depends on your carrier.

Verizon - no

AT&T - yes

I'm not sure that the hardware on an i4 will allow multitasking besides having music playing (which is done by a separate dedicated chip) while some other app is running.

In my i5 I do know for a fact that I can do other stuff concurrent with the phone call going thru whatever handsfree I have available at the moment.

If you needed to know ASAP couldn't you've have done a quick test on your iphone?

Good point.