Does Google only match tech company offers? Do they need to see actual offer letter?

Yes

Yes and depends on manager if they don't think you are a star they won't match

no, they dont even match all tech companies

Thanks for the input!

They recently asked to see my fb offer letter

We just discussed this in another thread here. Most offers start out verbally until you accept. So in that case you'd have nothing to show them.

I dont know now. But they did (almost) matched my Citadel offer