Every small, well-funded tech company ever has claimed that they weren't interested in acquisition. I certainly don't think that will keep the M&A folks at the big tech companies from chatting up Snapchat's investors.
For the second part, Google makes billions figuring out how to get ads in front of its users. I'm sure they'd be able to do something for Snapchat.
One other thing to consider: Google is sitting on something like $56B (and growing) in cash and short term investments. They could set $4B on fire and it really wouldn't alter their balance sheet significantly. Given its big push into "social" over the past couple of years, I could make the case that it's worth spending some of its cash to try and acquire a bunch of (admittedly fickle) users.
For the second part, Google makes billions figuring out how to get ads in front of its users. I'm sure they'd be able to do something for Snapchat.