THREE RHYMING RIDDLES

1)
It comes uninvited,
But not through the door;
It comes in a can,
And you can buy it at the store.

2)
Pulled apart or drawn together ,
We let in the light or shut out the weather.

3)
Born in one,
Alive in two,
Dies in three or more.
Once it is spread,
It can never be what it was before.

HINT:
1. The same word, but with two different meanings, answers both parts of the riddle.

Answers:

1. SPAM 
2. Curtains 
3. A secret or confidence