When a miner validates a block, does the block contain all transactions in Bitcoin for that time period? So does a miner validate an individual transaction between two parties, or are they validating transactions between all the parties in Bitcoin for that time period.
When you read examples about a transaction in Bitcoin, it makes it seem like each individual transaction (e.g. 1 Bitcoin from Bob to Alice) is its own block, validated by a miner.
So does a miner validate an individual transaction between two parties, or are they validating transactions between all the parties in Bitcoin for that time period.
A full node checks all transactions it hears about on the network, to ensure they are valid. If they are not valid, they will be discarded and ignored. When mining a block, a miner will use a full node to select only valid transactions to be included in the block template.
No. For example, I can make a TX now, a block can be found after the network pretty much all sees it but the miner doesn't include it (many reasons why this can happen, most likely one being it's a low fee TX and the block is already filled with higher fee TXs). It will then remain in mempools for varying amounts of time until a miner does include it in a block at some point in the future. (Sometimes it will never end up in a block. If the TX fee is 1s/b and the network is clogged for days on end it will probably being to drop out of mempools and never be included).