The difference between ONE ONES

I read about an interesting rule which help us a lot

and I thought to write here

The difference between ONEONES

1-
one=a,an

?Would you like a chocolate

Would you like one

chocolate=one

?I need a pen.Have you got one

I don’t like the black coat but I like the brown one.

2-
ones=plural

?A:Which keys are yours
B:The ones on the table

I don’t like the red shoes but I like the green ones

?These cups are dirty.Can we have some clean ones