Template argument deduction Doesn't Work for Function Template

I am trying to understand how template argument deduction works in C++. And so writing out different examples. One such example which doesn't work and i can't understand why is given below:

#include<iostream>
template<int var, typename T>
void func (T x)
{
    std::cout<<x<<std::endl;
}

template<typename T>
void SomeFunc(T a)
{
    a(6);
}
int main()
{
    
    
    func<5, int>(10);//this work as expected
    func<5>(20);//this works as well using template argument deduction
    
   
    SomeFunc(func<5,int>) ;//this works as well
    
    
    //the next two calls doesn't work
    
    SomeFunc(func<5>);//this doesn't work. Why doesn't template argument deduction works here
    SomeFunc(func<5>(20));//this doesn't work either.
   
    
    return 0;
}

In the above example, the statement SomeFunc(func<5>); doesn't work. My thinking is that when the compiler tries to instantiates SomeFunc<> it needs its template type parameter. But we have passed func<5> as the function call argument without actually calling(specifying the call argument to func itself) func so there is no way to deduce the second parameter and so it doesn't work. My first question is that is my analysis of why this call fails correct? If not then why doesn't it work.

Next in the statement SomeFunc(func<5>(20)); i have specified the function call argument 20 to func which was not specified in the previous call. But still this statement doesn't work. Why is this so?

While reading about template argument deduction i also came across the following statement:

Deduction only works for immediate calls.

But i could not understand what the above quoted statement means. It may have to do something with the fact that complete type or incomplete type used as template argument but i am not sure.