UK is 220v
120V appliance will not work on 220V. Use an instrument transformer or voltage regulator to adjust the high voltage to the desired level.
You don't, at least, not legally.
If all the components are rated to 220V, yes. Keep in mind that if the appliance was designed for 110V it may arc if 220 is run through it. If you don't know the device can handle 220V, don't run it at 220V. Chances are it was manufactured cleaply and cannot handle the extra voltage.
Using a 120V heat element with a 220V supply is not advisable, even with a rheostat, as it could damage the element or create a fire hazard. A rheostat can reduce voltage, but it may not provide consistent or safe operation under varying loads. It's best to use a heat element rated for the voltage of your supply to ensure safety and efficiency. For a 220V supply, look for a compatible 220V heat element instead.
Brazil has a nominal voltage of 220/380V.
No, 120 v is not enough.
This type of a transformer is known as a step up transformer.
To rewire a 220V lamp for 120V, you will need to replace the existing 220V bulb with a 120V bulb that is compatible with the lamp's socket. Next, you will need to install a 120V compatible power cord that matches the voltage requirements of the lamp. It's important to refer to the lamp's manual or consult with a professional electrician to ensure the rewiring is done correctly and safely.
nothing
220 volt will use less energy.
You can surely buy one on eBay, yes.