Firstly, you might wish to identify the model of your radio clearly if you want specific help on this forum. Tamiya tanks sold by US vendors do not come packaged with radios. Likely, you've got your kit from somewhere else, so it would be helpful to know what radio model you have.

Secondly, you likely have a radio problem and not a tank problem. You may need to reverse your servo signals using the radio to correct the reversed tank controls. See my photo attached for where the servo reverse switches normally are on a typical Tamiya radio transmitter. FYI, Tamiya has recently released a "Fine Spec" radio that looks different than the radio pictured below. You might have that one instead. I suggest you read your radio manual thoroughly, or do an internet search for how to reverse servos on a radio transmitter. Should yield some interesting facts for you.

Lastly, your radio is 2.4ghz, and 2.4ghz radios do not need the receiver to be hardwired to the external antenna to operate. Your tank kit was built for a radios that needed a hard wire connection from the receiver to the antenna mounted on the tank body.

Enjoy!