The three years run from the date of birth or, where relevant, from the court or administrative decision, not from the day you ask for the leave. It may be taken in instalments.
If another child is born, or another relative gives rise to a new leave, starting that new one ENDS the leave being taken. They do not stack.
There is no unemployment benefit during this leave. Article 267 of the Social Security Act lists the legal situations of unemployment and this leave is in none of them: the contract is alive, merely suspended.
Change the type of leave
The five types in article 46 are not variants of one thing: they change the right, the reserve and the contribution all at once.
Educational estimate based on the consolidated texts of the Spanish Workers' Statute and the Social Security Act. It does not constitute employment advice.
Your collective agreement may improve any of these periods, and article 46.6 allows further types of leave to be agreed. The public-servant regime is a different statute and is out of scope.