1. Is this laptop (yours, your's)?

Is this laptop yours? Although adding an apostrophe is normal when referring to example (is this laptop Kieth’s? etc.) it would not be used in the situation “your.” It would also NOT be used with “her” or “him,” instead it would be “is this hers” or “is this his,” respectively. “You”/“she”/“he”/“me” are four words I can think of that DON’T use the apostrophe and ownership s, instead having different endings depending on whose it is.
More examples:
“Is that laptop YOURS?”
“Is that laptop HIS?”
“Is that laptop HERS?”
“Is that laptop MINE?”
In all of these, you do NOT have the apostrophe.
I wish I could give an explanation but honestly, as a native English speaker and avid reader, I just know this rule by heart. Just like how I know that you have one mouse but two mice, it’s a change-up of words that someone else could probably explain a lot better; however I am certain in my answer, just not a detailed explanation.
Hope this helps :)