NFT Id using erc-1155

Question

I am bit confused regarding NFT implementation usng ERC-1155 because of newbie in NFT, by defination, there can be one instance of one NFT, there is one uuid per artwork. But in ERC-1155, I can set X amount per ID, so

1. This NFT thing, having one instance or amount per UUID will be managed on App side or there can be multiple instances of one uuid?
2. If I mint a token by setting token ID as uuid and path of actual image in metadata file. What if that image file replaced as that is not on Blockchain?
3. How can I setup commission while minting NFT using ERC-1155, or it is again to be managed on app side?
4. Is there a way if I want to prevent sale/purchase outside my app?

Answer 1

1. The point of ERC1155 is that each NFT id has a distinct balance of tokens. You can see it as a fungible NFT.
2. This is a feature, which is often used on NFT collection reveals for example. At first, NFTs have a temporary image, and on reveal owners change the baseUri, which changes the images of all NFTs. Concerning the image storage location, usually developers use IPFS, which is a file storage blockchain so data there is immutable.
3. There is a ERC2981 standard, which allows you to set royalties, but it really depends on the marketplace if it will take it into account or not. So in most cases you have to define it in app.
4. You can prevent NFT transfers in smart contract by updating _beforeTransfer and only allowing your contract to execute transfers. However I would not recommend this as the collection will seem broken on other apps.