Nice explanation and link on how the blockchain is built on earlier blocks and how it cannot be tampered with, as previous blocks will change the hash of the next block.

How does current difficulty of mining come into account in the creation of a new valid block? I´ve noticed that you can find the solution to a block with much higher difficulty than the static difficulty you´ve configured your miner to use? This is great since it makes it possible for miners with lower hashrates to have a chance of submitting a valid block, but how is it possible?