There’s not really any such place. We’ve looked in Antarctica, we’ve looked in Greenland, and all parts in between. If there were signs of tool-using intelligent dinosaurs equivalent to even H. ergaster, we’d have found them.
No. See this earlier thread on ancient civilizations for a discussion of why subduction isn’t the gotcha laymen seem to think.
And do you think the geology of the Himalayas isn’t well-studied?