In general, yeah you can choose any arbitrary address that you want for null address.

The reason you can do that is because it is almost impossible for you to choose a random address that somebody already has a private key for it. Let's do some math to prove it, an address is 256 which mean it can go up to 2^256. The earth population at this time (12/2021) is about 7.9 billion but i will make it 8 billion for ease in calculation. Assume every person in the planet has 100 private key corresponding to the address they have. Then the possiblity that you can choose an address that they already choosen is about 10^-66 (https://www.wolframalpha.com/input/?i=800%2C000%2C000%2C000+%2F+2%5E256).

The possiblity that you win a Powerball is one in 292.2 million, roughly 10^-9 (https://www.thebalance.com/what-are-the-odds-of-winning-the-lottery-3306232). So you will have to win Powerball roughly 7 times in a row to even get a chance in picking a random address that somebody already has the private key given that everybody on the earth have 100 private keys

No, there are no exceptions and it's not possible to deploy a contract to the zero address. It's cryptographically impossible as it would mean that someone could brute force a private key corresponding to the zero address. It's typically computationally infeasible to generate a deployment address that has more than a few desired bytes.

The address you mentioned on polygon is actually not a deployed contract. It just represents the native token of Polygon, sort of a placeholder to be recognized as the MATIC/POL token for certain contract logic. Other EVMs have similar placeholders for their native token.

gm u/kwizzn, the OpenZeppelin Burnable ERC20 standard details that burnt tokens will emit a transfer event to the null address, however its balance will be reduced from the total supply hence the balance being 0.

You could consider querying its initial total supply, versus its current one to determine the amount of tokens minted/burnt.