Questions about the Executable Beacon Chain Proposal

I am reading the executable beacon chain proposal here, and I have a couple of questions and I would appreciate if someone more versed in the Ethereum technology stack can help answer.

I reproduce the snippets I am confused about, and the questions I have below.

In the proposal you have the following:

Eth2-client sends an executable data to the eth1-engine. Eth1-engine updates it inner state by processing the data and returns true if consensus checks have been passed and false otherwise. Advanced use cases, like instant deposit processing, may require full transaction receipts in the result as well

Questions: 1. How can Eth2-client send executable data to the eth1-engine. Is it not the case that the Eth2-client only have knowledge about Beacon blocks? How are those executable by eth1-engine? 2. I thought the idea is to move consensus functionality to the beacon-chain? How come it is possible for eth1-engine to still be able to check if consensus rules are passed?

Also, you have:

Eth2-client sends previous block hash and eth1 state root, coinbase, timestamp and all other information (apart of transaction list) that is required to create executable data. Eth1-engine returns an instance of ExcecutableData.

1. How can an Eth2-client send things like eth1 state root, coinbase etc to the Eth1-engine? These pieces of information look very eth1 centric, how does the Eth2-client come to have this pieces of information?

Then later we have:

We modify process_block function in the following way:

def process_block(state: BeaconState, block: BeaconBlock) -> None: process_block_header(state, block) process_randao(state, block.body) # process_eth1_data(state, block.body) used to be here process_operations(state, block.body) process_executable_data(state, block.body) 

Questions:

1. What exactly is the end result of the Eth2-client processing executable data? Why should the Eth2-client process executable data? And what things would processing this executable data bring about?