Does wp-cron run all tasks scheduled at the same time together or one after other?

I am developing a plugin and want to add a cron task(let's say cron_task_test) but have a doubt. In case 15 tasks(they may be scheduled by multiple plugins or the user himself) are scheduled to run at a time along with my task(cron_task_test), will wp-cron pick them one by one i.e. pick another task after first has finished or if the first task has taken more than a minute? Or does all will be fired one after another

In short, how do cron_lock works? In case it executes one after another, will not the main cron thread running all tasks one by one itself exceed maximum execution time limit of the server(generally 30 seconds)?

What will happen if any other cron task before my task(cron_task_test) has thrown an error or exceeded time-limit? A