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The general convention for naming a variable _ within a lamda function is to indicate that you are not going to be using the param that will be passed into the lamda but the consumer of the lamda still expects to pass in variables.

That being said...javascript doesn't require you to do this and would actually work just fine if both listeners expected no arguments.

It should be noted that the _ in

await web3Modal.connect() already returns a provider; try to use that one instead of new ethers.providers.Web3Provider(instance);

You can set the gas limit with an object as the last argument, for a simple transfer transaction, you could do something like this:

The returned Wallet object (docs) contains the private key and the address of the wallet. However, the address generating algorithm is universal across all networks. So if a private key 0x123 generates an address 0x456, you can always use the same 0x123 private key to sign transactions from 0x456 address on all networks - the mainnet, Ropsten, Rinkeby, etc.

The network on which you broadcast the transaction depends on what network is your provider connected to. So if your want to limit on what networks the app can send transactions, you need to validate the provider's getNetwork() returned value (docs).

Ad the options param: In the createRandom() source code, it only uses the param to affect the pseudo-randomness of how the private key is generated. But again, it's not related to the network(s) on which you're going to be using the wallet.

Please accept my apologies. The code above queries the balance in eth of the Ethers library, not the Metamask wallet of the signer.

Here is the correct code:

Looking at the code, format will definitely return a string in all cases.

From your code excerpt, it's not clear what you're logging in the console.

It should be something like:

When you create a transaction with Ethers.js, you get back a TransactionResponse that may not be included in the blockchain yet. Therefore it doesn't know what logs will be emitted.

Instead, you want to wait until the transaction is confirmed and you get back a TransactionReceipt. At this point the transaction was included in a block, and you can see which events were emitted.

but I couldn't figure out how to get the token name like BTC, USDT, ...

Because you don't.

You need to provide a token name - address mappings yourself, or ask from the user.

When you are are running the method attached to filters you are correct data that allows you to look up the events.