Is there any way to Tether through wifi? I have a desktop without a wifi card. Can I tether my computer to the phone but the data should go through wifi rather than the plan?

I want  PC - USB -> Android phone - Wi-Fi -> internet
There's an app called Easy Tether (XDA questions about doing it) which can do that. You basically just set up USB tethering and disable the "use LTE" or "use 3G" settings, to force it to fall-back to wifi. Personally it seems a bit silly to do that, when a $10 wifi adapter that plugs into the PC with USB would likely work better.. but yes, you can in theory do it.