Different outputs from Crypt(3) and CryptoJS

Question

I am hashing passwords in MariaDB using:

ENCRYPT('password', CONCAT('$6$', SUBSTRING(SHA(RAND()), -16))

Which produces something like:

$6$3b502db443d64283$BNSYWsf3T0e4xT23GJW/QPpKvzLidio5zk9v7kCE.wk4dtNo4avMzBxvqoWc0Y5ihj/zVwtGCwZRfTFur0BnI1

The format here is $6 meaning SHA512, then the $salt$ and then the computed password hash. So the computed hash alone is

BNSYWsf3T0e4xT23GJW/QPpKvzLidio5zk9v7kCE.wk4dtNo4avMzBxvqoWc0Y5ihj/zVwtGCwZRfTFur0BnI1

As I understand it this uses crypt(3) in the background. If I write a short bit of C such as:

#define _GNU_SOURCE
#include <crypt.h>
#include <stdio.h>

int main() {
  char * blah = crypt("password", "$6$3b502db443d64283");
  puts(blah);
}

Taking care to put in the same random salt as the RAND() function generated for MySQL and prepending the $6 to use SHA512, then I do indeed get the same result:

$6$3b502db443d64283$BNSYWsf3T0e4xT23GJW/QPpKvzLidio5zk9v7kCE.wk4dtNo4avMzBxvqoWc0Y5ihj/zVwtGCwZRfTFur0BnI1

Again the computed hash itself is:

BNSYWsf3T0e4xT23GJW/QPpKvzLidio5zk9v7kCE.wk4dtNo4avMzBxvqoWc0Y5ihj/zVwtGCwZRfTFur0BnI1

Now if I use CryptoJS and wanted to compare that Hash in JS code rather than in the DB (or in - heaven forfend! - C), then I find that I have a problem. For example here is my CryptoJS code:

var CryptoJS = require('crypto-js');
var SHA512 = require('crypto-js/sha512');
  console.log(SHA512("3b502db443d64283password")).toString();

I prepend the salt to the password as this function takes only a single argument. The result is:

105865ba5bf0649410927131204a1228260e59e95b1b53942001b98835dca4aedfe7039a00060fdba8531c44c83cd3b7bec4864865915938d2ed7ed477254f61

Ok. So I recognise that that is a Hex encoding of the Hashed password. So I'll change the encoding...but to what? I'll try Base64:

  `console.log(SHA512("3b502db443d64283password")).toString(CryptoJS.enc.Base64);`

The output is:

EFhlulvwZJQQknExIEoSKCYOWelbG1OUIAG5iDXcpK7f5wOaAAYP26hTHETIPNO3vsSGSGWRWTjS7X7UdyVPYQ==

I'm starting to see a problem here. The encoding used by crypt(3) isn't base64. What is it? I look in the man page:

The characters in "salt" and "encrypted" are drawn from the set [a-zA-Z0-9./].

So I'm left with these questions:

1. What is the encoding used by crypt(3)? Is it a standard or just a chosen character set.

2. Is there any way to compare hashes generated with two different character sets like this? I mean is there an underlying representation they share of the hashed password? Can I access it?

3. How do I know how many rounds each function is making? Is there any way to know without examining the source code?

4. Is my assumption that I prepend the salt correct when using CryptoJS?