[Grammar] but I knew before I went that I didn't really want to have a serious relationship wit

[nininaz]

Hello all,
Can we use "know that" in the following way?
Is it kind of a grammar rule to put an independent clause between "verb + that", such as think that, see that. ? I can't figure it out.

"It was a really terrible vacation.It was m y fault. I mean I wanted to go to Thailand, but I knew before I went that I didn't really want to have a serious relationship with Joe. And the vacation just showed me how different we are."

 

[nininaz]

There is no obligation to put subordinating 'that' immediately after the verb.

Wow! Such an amazing tip. I didn't know about it.
Is it true about all of these kinds of verbs?
So I can say:
but before I went ,I knew that I didn't really want to have a serious relationship with Joe.

 

[nininaz]

Can I ask in the following sentences, both of the pronoun "it" is dummy-it?
It was a really terrible vacation.It was m y fault.