Can i use bluetooth speaker while charging or not?
Yes, Of course,
You can operate the speaker by battery instead of the USB AC adaptor by charging the speaker before use.
Plug the USB AC adaptor to an AC outlet. Do not use any USB AC adaptor or micro-USB cable other than the supplied ones. The CHARGE indicator lights up in red while charging.
If you do have branded speaker one you can try out. But never try this with a non branded portable speaker.