You mean to change the connection type of your hardware?
Blynk only works with a valid connection…
To change the wifi credentials there are better solutions that use a widget…
There is a library that lets you know if a double reset was performed (one reset after another in a short period of time) and, together with this, you can use another one to configure a wifi manager to modify the Wi-Fi connection data. With this you’ll make a special programming mode without waste any phisical pin. I use this on all my projects.
Are you sure you want to remotely change how a device connects? If something goes wrong … how do you fix it if it’s out of line?