You can use Unity personal tu publish a game on every platform for free but if you start making a revenue up to $100k per year you need to pay an annual plan, which starts at $40 per month.
Here you have all the info for that in their site Info of Unity Plans
On the other hand you should pay a developer license of each platform to publish. Every platform ...
I believe this would be from futile to impossible. Unfortunately it's quite common to see clones of other games. Unless that person is using exact copies of your assets from your game this game won't be considered "stolen".
You can try to lawyer up, but consider amount of clones out there, even with same name, but released on different platform.
You can't just "flip velocity over y". To further that point, its obvious to see on the left and right sides of the box you would not flip over y, but instead flip over x.
On the corners you need to flip over a diagonal direction. This is where it becomes less obvious how to flip it. But it's still quite easy:
What you need is a function to flip ...