problem description
after taking a look at css modules, there are still many places I don"t understand. I hope you can give me your advice
.principle
css-module achieves local scope by escaping class to a unique class name in the form of hash.
my question
question 1
 does the generated hash form class name change each time you build? 
 for example: 
<div className="{style.block}"></div>
hello boys
is compiled into:
<div class="block_xyT5N"><div>
hello boys
I modified the p tag to add a style to it
<div className="{style.block}"></div>
<p className="{style.parag}">hello boysexcuse me, will the block_xyT5N class name generated by the original div change after I change the style of the p tag and rebuild it? Why?
question two
won"t hash collisions occur in hash formal class names? Won"t there be a duplicate name? For example, there are hundreds of class in the current file, while hash generates a general configuration:
{
    test: /\.css$/,
    use: [
        {
            loader: "style-loader"
        },
        {
            loader: "css-loader?modules&localIdentName=[name]-[hash:base64:5]"
        }
    ]
},configuration only takes the first five characters of the first hash. Does this guarantee no repetition? Isn"t this a combination of 100, 000 or 1 at most?
