Does your computer's adapter support Gigabit?If yes, you may force the speed on your pc to 1000Mbps. If no, we can not get 1Gigabit connection even the router and cable support that.

Login to web UI of TL-WR740N, go to Network --WAN and change MTU size to 1400. hope it work.

After you update the firmware, you need to reconfigure the router. Or before you update it, you should backup the setting file. If there is no BT infinity option, you may choose other to put ISP info...

No matter wired or wireless connection often drop? Have you updated the latest FW? Make sure the FW is the latest one.

There is an option Allow Guests to Access My Local Network, do not click on that.

It's mainly designed to place on the table, so there is no any holes on the device. If we want to attach it to the wall, we may need to tie up to other object.