Can you use the Internet ONLY with a Powerline adapter via cable?

If I have a Powerline adapter in my room and have connected it to my laptop via ethernet, can I still transmit a strong wireless signal from the Powerline adapter, e.g. For my cell phone?

If the Powerline Adapter also has a Wi-Fi module at the same time, you can.

If you have a powerline adapter that has Wi-Fi and cable connection then yes.

Sure, but why a strong one? A normal weak does it too.

Depends on the adapter. There are both variants: only LAN connection and LAN + WLAN.