Theoretically, the range extender should be cable to connect to wifi and give internet via Ethernet cable. But there are some limitation: 1. the wifi from your Dongle should be using normal wireless security type, not portal authentication. 2. that connection may be unstable because the whole internet relies on wireless connection 3. the speed wouldn't be as fast as cable connection.

I think i should clarify, at my place my dongle based internet connection is a 4G connection and way faster (about 4Mbps) than my wired connection (about 1Mbps). Also its a lot more stable than my wired connection which keeps dropping and reconnecting. Hence the need to do the same. My office requires a stable and consistent connection, but i dont want to get one 4g connection per PC nor do i want to install WIFI on all the PCs at my office. Now another feature of this dongle is that it is not a usb based dongle. It takes a 4g sim and acts like a wireless access point. Now i was wodering if i cofigure the TPLink extender to take the internet connection over wifi (the dongle will kept right next to the extender) and i connect the ethernet port of the extender to a port on my router (not sure which one, the WAN port or the regular SWITCH port) then my PCs will be able to connect to the internet using the same.

Is this workable ? and if so should i connect it to the WAN port or regular SWITCH port of the router.

Haven't tried such scenario. You may borrow a device from your friend to test if possible. Either the WAN port or the LAN/SWITCH port would be fine.