Very Tricky Question

[dalfred]

Hello to all, it's my first time here

Feeling good already.

need some advice/info/correction

What is correct?(and WHY is very Important!)
I'm talking to the director of Wall Street Institute for English on Friday.


No sooner had I opened my front door ... that something was wrong.

did i realize
than i realized

(fill in the dots) (why)


And one more

Sorry you didn't find me at home. ... out to do some shopping.

I've gone (why)
I'd gone (why)

I failed on both. But i am 999 million percent sure (don't know why) that 'did i realize' is correct.Just can't explain it.
And 'I've gone' is correct because i left a note.(or not?)

Cheers
Donald

[Tdol]

1 It is 'than' because it goes with the comparative form 'sooner'.
2 I'd gone- this is because this action, leaving the house, was before the other past action.