Eldeeb, "leader boards" show players' scores and are meant to be updated whenever a score changes. For example, if you are playing a game online with many other players, everyone's score is displayed. The person in the lead (the leader) is listed at the top.
Without a context I can't say with certainty what "lock orientation" means but "lock" means "to hold in place" or "unable to move." "Orientation" typically means the direction someone, something OR an idea is facing. So my guess is "lock orientation" means whatever direction something has chosen can not be moved or changed. I'm guessing you are either using a phone or software which will allow you to choose the orientation (direction) of what you're viewing. "Lock orientation" on your smartphone will allow you to look at the screen, no matter how you move the phone, and the screen will not move.
Finally, I don't know what "Vegas cumulative" means, and I'm willing to guess it's a specialized phrase. "Cumulative" is a way of describing additions, which may or may not end in a total. For example, my friend likes to "accumulate" DVDs. This means she has a collection of movies she keeps adding to. My best guess for you is "Vegas cumulative" refers to points adding up in a game. Hope this helps.