I put "it depends" but it isn't really true. The truth is that after five minutes of trying I can't decide which probably means that it's one of those unusual words where neither syllable carries a stress ( or both have equal stress).

Initial stress only, though I have free variation between CON- and CONG-. I've never heard con-CRETE as a noun or adjective, even as an American pronunciation, though it is the (little-used) verb.

Variable stress usually happens in phrases to avoid clash of neighbouring stresses: so if you normally said con-CRETE you might say CON-crete EV-idence. Test it with a following noun that doesn't have a clashing initial syllable: do you say con-CRETE pro-PO-sal?

Difficult, yes. But try stressing the final syllable - as in "discrete" and you will probably agree that the stress falls on the first. Or it does in the south of England, anyway!

I just can imagigne what the other example would sound like so I plumped for the first option.

I pronounce it just as you do, wordnerd.