That depends on the query. SQLite tries to use LIMIT to restrict the amount of reading that it does. It is often successful at that. But some queries, by their very nature, logically require reading the whole input in order to compute the correct answer, regardless of whether or not there is a LIMIT clause.

That's what it does, but if I'm not mistaken (at least in my experience with MariaDB) it'll also return immediately once it ran up to the limit and not try to process further rows. If you have an expensive subquery in the SELECT (...) AS `column_name`, it won't run that for every row before returning the first 10 (when using LIMIT 10) unless you ORDERed BY that column_name. Other components like the WHERE clause might also require that it reads every row before finding the ten matches. So mostly yes but not necessarily

The limit clause isn't official/standard ansi sql, so it's up to the rdbms to implement. Your assumption is true for bigquery (infamously) but not true for things like snowflake, duckdb, etc.