Surprised Round doesn't exist, it's a surprised condition.

https://rpg.stackexchange.com/questions/124807/when-exactly-does-combat-start-and-surprise-take-effect

https://rpg.stackexchange.com/questions/150904/is-there-a-surprise-round https://slyflourish.com/surprise.html https://www.flutesloot.com/surprise-rules-dnd5e/ http://dmsworkshop.com/2018/07/13/things-you-didnt-know-about-dd-5e-the-surprise-round/ https://roll20.net/compendium/dnd5e/Combat#content

Stealth

https://www.reddit.com/r/DMAcademy/comments/p253z4/when_do_you_roll_a_stealth_check_for_enemies_that/ https://www.enworld.org/threads/how-does-stealth-work-in-d-d-5e.681156/ https://olddungeonmaster.com/2014/12/28/dd-5e-stealth-and-hiding/