Can someone guide me to understand this sentence. I wrote Das sind Kleine and got wrong. Thanks in advance

"small" is used in this source sentence as an adjective and not as a nominalization (as you suggested) as in "das sind die Kleinen". Also, the verb is in the plural form which is not reflected in your suggestion. More on this here: http://en.wikipedia.org/wiki/Nominalization

Das sind klein - possible?

Could you say "Dies sind klein" as well?

"Das sind klein" not accepted? I saw they used "Das" with "sind" usually, why can't I?

Why Die instead of Das?

I think (don't quote me) that it's die because it's plural (sind). You would normally use die for plural 'the'. Someone native could shed some light on the issue?

I am not certain,but here is what I think. By "those", they mean it is plural. "Die" is "the" for plural nouns. "Da" means "there"(I think). So "Die da", I'm guessing, [Noun(Plural)]over there(is small). Please don't correct me if I am wrong.

Why can't it be "Die dort sind klein"?