Someone’s is correct because Someone is always singular. Someone’s is the possessive form of the word which means “Someone” owns something. Someones is incorrect and should not be used in English.
We use Someone’s in English when we want to show that something belongs to some of the people that we are talking about. This is common to use when we are talking to a group of people.
Is someone’s house here the same colour as mine?
Is someone’s daughter called Jane?
Somone’s can also be the contraction of someone is or someone has.
Someone’s talking about me, I know they are.(is)
Someone’s already found the treasure.(has)
Someones is incorrect because Someone is singular and therefore we do not need to make “Someone” plural in English.
Someones’ is also incorrect in English because when we add the apostrophe after the s, it is because the word is already plural. As we have already said above, Someone can’t be plural so for this reason Someones’ is incorrect and should not be used in English.
Is there an apostrophe in Someones?
Yes, there is an apostrophe in Someone’s because Someone’s shows possession.
I have no idea who ate the cake, it must have been someone.
Someone’s car is parked in front of mine.
Is it Someone’s lives or Someone’s life?
“Someone’s life” is correct because “Someone” is a singular word.
Someone’s life is at risk!