No, it is not possible to directly fit a Dynojet Power Commander 5 (1020-1782) designed for a Yamaha WR450F (year 2013) onto a Yamaha FZN250 (year 2019). The Power Commander is specifically designed to work with the electronic control unit (ECU) of a particular motorcycle model and year.
The WR450F and FZN250 have different engine configurations, fuel systems, and ECUs, which means they have different requirements for fuel and ignition mapping. Therefore, the Power Commander designed for the WR450F would not be compatible with the FZN250's ECU and would not provide the intended performance enhancements.
If you are looking to optimize the fueling and performance of your Yamaha FZN250, I would recommend looking for a Power Commander or fuel management system specifically designed for that model and year. Dynojet or other aftermarket manufacturers may offer a compatible option that is designed to work with the FZN250's ECU. It's important to use a fuel management system that is specifically designed for your bike to ensure proper functionality and performance improvements.