Interchangeable Keywords in title and headings

Are keywords in titles and headings interchangeable or do they have to be in the exact same order as per google adwords. I am trying to naturally combine 3 keywords in my title, h1 and h2 to rank for all 3. Would each of the 3 individual keywords have to have an h2 in the content? Is this safe to do or not recommended?

"pie apples" a.k.a. the apples used in pies is a very different search than "apple pies". A "blue sky" is very different search term than the color "sky blue".

Also... Usually a page will rank for one search term best and other search terms not so well. The best practice if you need all three search terms is to target them separately giving each one its best chance to rank best on a page.

For example: For the search term "apple pies" what should rank better in the search results "a page that is 100% about apple pies" or "a page that is about apple pies, blueberry pies, pecan pies, banana creme pies,..."? The later should rank better for a page about pies in general, but should not do as well for a search specifically about "apple pies"