Please let me know some general concepts of blockchain network systems

Hello,

I have been playing some tokens on the Ethereum blockchain network,
and then, I have just moved to the Binance smart chain network.

I could see, the payment unit is generally ETH on Ethereum netowork. In contrast, BNB is used on Binance smart chain network.

From these systems, some doubts came out from me,

  1. I was wondering if I can make the payment system with ETH and BNB together on either the Binance chain network or the Ethereum blockchain network? If so, are there any source codes for this?

  2. If my personal token(let's say ERC-20) is deployed on either the Ethereum blockchain network or the Binance chain network, am I able to use my token as a payment method, connecting my token to a new smart contract which is going to be deployed on the different network from the network which my token is deployed on. (so, if token is on the Ethereum network, the new smart contract will be on the Binance chain network)

  3. The way of deploying smart contracts onto the Binance chain is pretty much similar to the deployment of smart contracts on the Ethereum network.,
    Here is a thing, I used the truffle with React and send the 10000000 joger = 0.1 BNB. as I know, 1 BNB has 8 decimal and Jager is equalt to 0.00000001BNB.

When I click on the button to send '10000000'(10^7) to another address, my metamask came up and BNB price indicated just 0 BNB . I thought it would be 0.1BNB. Afterwards, I just changed the value to '100000000000000000'(10^17), then I could see 0.1BNB. It seems to follow the decimal of ETH which is 10^18.

However, I do not know why it is ... , even when I deployed my smart contract onto the binance network, I could see the unit of cost was ETH on my VS code command window, But actually, The amount of BNB was deducted on my metamask wallet.

Please, improve my knowledge