Usage of anohter

Are the following sentences correct?
Another boy entered the room. OK
Another boys entered the room. No
Another three boys entered the room. OK. The boys entered the room in a group of 3 together. Or three more boys entered the room.

Thanks, AlpheccaStars.

I understand the third sentence is correct. I have no perplexity about it.

Gotcha.

But I think the second sentence is also OK because it could mean the same as the third. I think the second is correct in case it means the third or in case I use it to mean the third.

Am I wrong?

Just say,

Other boys entered the room.

Thanks, wq.denis.

I know your sentence 'Other boys entered the room.' is correct.

But how about the second sentence? Is it absolutely incorrect? Or is it correct in some specific situation?

It is incorrect, because "another" is singular. It cannot be followed by an unqualified plural noun. If followed by a number + plural noun, then that refers to a single group or quantity.

He is lucky; he just earned another million dollars on the quiz show.
We put another five chips in the pot.

Thanks, AlpheccaStars.
I understand the third sentence is correct and why it is correct. I have no perplexity about it.
Gotcha.

But I still have a question about the second sentence.
The second sentence is as follows.
Another boys entered the room.

Suppose you are having a dance contest. Each dance team is composed of three boys with no exceptions because three

Yes, that's still wrong.

Another team of boys, another set of boys, another group of boys, another three boys, but NOT another boys.

Woo-oow!

English is so tough about numbers!

But it's so nice and exciting!

Gotcha!

Thanks!