Which is correct spelling Gods or God's?

Answer 1

Its God’s will or is it, it’s God’s will?

Answer 2

Both could be correct, depending on the context.

The capitilized proper noun God is used to refer to the Christian and Jewish God. So you wouldn't use the capitalized form without an apostrophe because it makes it plural which doesn't happen with most proper nouns. You could only do this if you were using the common noun 'gods' which has a completely different meaning.

Probably you are wanting to use the word in the possessive sense - referring to something that God is or has ...such as God's mercy, or God's creation. You must always use the apostrophe and then s with this word. ( There are other words where this rule doesn't apply....but that's another English lesson...and doesn't apply to the word God.)