In theory, you can of course use any language you like, but there are a few commonly used ones.
From your list it would be c++ or c#, because if you actually have the interest long term then those will be the languages used by the various "big"/well known/used engines.
I would suggest c#, because it can be used with the Unity engine, which has an enormous community with help resources especially to start out and learn to program or game development.
On the other hand I would also suggest JavaScript. It isn't used for any of the big title development, but for all the *.io games like slither and so on. When looking at such games you will quickly notice that they are generally much simpler (for example 2D not 3D), because game engines are just simpler in JavaScript. While this is obviously limiting it might help to get something simple actually working, instead of getting stuck in extra complexities and additional features until you lose your motivation.
The basic programming you learn is still the same, so after you have learned a language you can quickly pick up most others.
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The answer is an Intruder Prevention System (IPS). An Intrusion Detection System (IDS) will detect an attack but will not block it.
For count digits, you could just convert it to a String and check the length
Sum digits, convert to string then seperate each character with charAt then convert it to numbers in the return statement.
Average digits you can convert it to a String and then convert them back after taking them apart.
A cell reference is also called a cell address.
