No, that just means someone sealed it after the fact. Usually they are just painted shut by landlords. If you want it to open again, you just use this tool called a window zipper: https://www.amazon.com/CRL-Window-Zipper-Deglazing-Tool/dp/B00QL57QSM

Look into double-hung windows. It's a thing. http://1.bp.blogspot.com/-HpSS5fG5FS0/UAswlXDDxAI/AAAAAAAADyw/sa-PF8HsKHw/s1600/double+hung+window.jpg

There are weights in both sides to keep it up. With bad maintenance over time, I'm not surprised the friction is failing to keep up the top sash without the lock. It's very common.

Nowadays with modern air conditioning and handling, people don't worry about needing double hung windows that often. But before, it was a key component of getting some breeze through the house.

source: I'm a certified window restoration specialist

Those do look like they open though I imagine there's some reason they were painted shut, hopefully it wasn't a good one! You'll want to cut away the paint and peel the caulking (or cut it if it doesn't peel). Amazon sells a tool that I've seen recommended specifically to cut paint around windows. I've been meaning to buy it for my own painted-shut windows when I get around to that project.

CRL Window Zipper Deglazing Tool https://www.amazon.com/dp/B00QL57QSM/ref=cm_sw_r_apan_i_7HZ2EBD1RNFZE35ME332

Once they're open, maybe repaint your sills with an exterior paint to beef up the water proofing (check for cracked old paint that hasn't been touched up while the windows have been sealed shut). Then take some time to air seal the windows with foam. Figure out what sort of gaps you have between the window and frame when it's closed and locked, then find a foam tape of appropriate thickness to fill that gap.

Don't use a hammer on windows.