Can I use "it" even though the subject or the object is plural?

Question

I want to confirm whether what I may have heard or read is correct, i.e. using the pronoun "it" even though the subject or the object that is being referred to is in a plural form. From what I may have heard or read, it's actually fine to use "it" even though the subject or object is plural. I should also apologise if I don't provide the link or the reference since I don't remember it.

These are some examples that sometimes make me confused as to which pronoun I have to use:

1. Suppose I see a lot stars in the sky, should I say "beautiful isn't it (the stars)" or "beautiful aren't they (the stars)?
2. When I notice a group of things, should I say "what are those" or "what is that"?
3. I have to explain three different points that are unrelated to someone, should I say "I can explain it to you" or "I can explain them to you".

It may look like I ask three different things, but I'm just giving examples to support my main question, if there's anything that needs to be edited or needs more clarity please do let me know and I'll edit the question right away.

Answer 1

All six of those sentences sound correct and natural.

In the first example, "it" would be understood to mean the view. In the second example, "that" would be understood as the group of things. In the third example, "it" could mean "it all", as in all the things that need explaining.