Is it possible use USB tethering feature of ios devices as similar to andriod? Connecting device over WiFi through WiFi-router and using that connection in another machine with USB tethering by not using mobile data.This is possible in android devices.

Just to make it more clear, I don't want to use my mobile data but I have a working internet connectivity by WiFi router, So I wish to use the internet connection in my laptop through my iPhone 6 plus which is connected to internet via WiFi (NOT BY MOBILE DATA),

However in android devices if device is connected to working WiFi connection it is possible to use that connection in any other machine through USB tethering(100% tested).Just need to if I can do this using my iPhone too.
Hope I am clear with question.

The main motive is to get the WiFi connected ios device connection to a machine just in case if the machine having a WiFi issue and Ethernet port problem.This is possible with android device through the USB tethering which doesn't uses the mobile data Only it uses the connection of the router and provides to the machine
No. You cannot do that with an iPhone. If an iPhone is on wifi, it will not share an Internet connection with another entity in relation to tethering. In fact, if you turn on tethering while connected to a wifi, it will disconnect from the wifi automatically before sharing Internet. 

I recommend that you instead pickup an inexpensive USB wireless adapter. I saw another one for as little as $20 (presumably not including shipping).