SQL Server Admin 2014 :: Disconnected From Listener In Availability Group (When Primary Failed)

I setup an availability Group. (Only 2 servers - Primary And secondary) -- 21 , 22

I also define an listener . IP .. 23

1- In First step I connected To Listener (23) And in a while I inserted A record to a table .

While 1=1
insert into Tbl_T1(f1,f2) Values (1,2)

2- in second, I Stop the primary .

- I expected this while whitout disconnect, continue.

3- The while code stopped whit this message :

Msg 64, Level 20, State 0, Line 0 A transport-level error has occurred when receiving results from the server. (provider: TCP Provider, error: 0 - The specified network name is no longer available.)

4- I execute again the script, And it worked in new primary.

My questions :

1- is the listener disconnected between switched primary and secondary ? OR have we data loss between switching?

2- I did some huge update on Primary that fill the Log fiel space. And in last Update I got this error :

Msg 9002, Level 17, State 2, Line 27

The transaction log for database 'Your_DB' is full due to 'LOG_BACKUP'.

Is this (Fill All space) a reason to switch primary? Or not ?