No, firstly 'will' and 'going to' are not interchangeable above a very basic English level, in which you first learn about them.
The other words all mean different things, and so are not interchangable.
Also, here is ''anybody'' in a positive sentence: "I'll talk to anybody. I love people."
Here is "somebody"in a negative sentence: "There's water all over the floor. Somebody didn't take their boots off!"
OK, there is a little bit of truth in everything you say, and a great deal of falsity. This often happens with baby grammar rules. The important thing is to learn what a rule means, not simply what it says. That is, you need to discover what is true about the rule.
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