Reset ISOLATION LEVEL to it's default for SQL Server >= 2014

Question

I read this topics:

SQL Server 2014 reseting isolation level

How do I unset/reset a transaction isolation level for SQL Server?

KB3025845 - FIX: The transaction isolation level is reset incorrectly when the SQL Server connection is released in SQL Server 2014

Entity Framework and Transactionscope doesn't revert the isolation level after dispose of Transactionscope

What does sp_reset_connection do?

And so many posts and blogs...

I have some questions about this topics:

1. I couldn't find a reliable reference from Microsoft sites that explain reset ISOLATION LEVEL in SQL Server 2014 and sp_reset_connection. How can I be sure that this happened and ISOLATION LEVEL reset to it's default value.

2. Does it correct that changing ISOLATION LEVEL in stored procedures, just have scope in the scope of the stored procedure? Doesn't it affect connection?

Thanks