Block time refers to the average time it takes to move on or find the next blockchain? coin block, this can be achieved through Genesis coin creation, Proof of Work mining and via the Proof of Stake consensus too.
Transactional data is permanently recorded into the blocks? - some other information can be added by signing transactions, blockchains? are essentially public ledgers but some coins and tokens have taken the choice to hide this data, there are some reasons for this with Privacy? being one of them.
Different blockchains? and their cryptocurrencies move along at different speeds and time-sets according to their individual overall designs, some are a matter of seconds with others into the minute marks.
The way blocks are organized is that they are added in a linear sequence over time as they occur, this becomes the blockchain?. As new transactions are being constantly processed by the miners?, once discovered (or solved) they are then added to the end of the blockchain?, sometimes the algorithm difficulty of solving the transactions becomes very high, this could be due to many miners? and their devices joining the network suddenly, or the amount of users and transactions filling the blocks? resulting in a delay being processed onto the next block - this is happening more and more with Bitcoin and some interesting real time charts and historical data can be found at: https://jochen-hoenicke.de/queue/#0,24h - you can zoom out to a longer timescale over a period, including all time, too.