Why were frames deprecated in HTML5, but not iFrames? After all, there is almost no difference between the two. In many instances using either of them would give the same output (pardon me if I am wrong)?
There's a couple of misconceptions in your post. First, the
Note 1: the
Frames (frameset) acts as document. It's removed because it breaks HTML documents structure and navigation. Eg. you have links in one frame, content in the other, you can't open link from the page in in a new window, you can't link to specific sub-page, etc.
On the other hand iframes won't break anything if used correctly because they're meant to sandbox content (eg. ads).