Need help changing volumes for bootup

I had to recently erase the data on my Mac book pro mid 2012 laptop. When I bought used it wasn’t freshly erased or anything but dude logged out of everything so at the time I just used it for internet browsing didn’t care until recently when it was basically hacked for lack of better words so I went to finally wipe the drive and start fresh. When I got it tho I had planned to do this gem and think I downloaded the upgrade OS on another volume that I didn’t select when it 1st asked me just guessing which volume it wanted to boot from and which had my data on it. You can’t quite tell both are unnamed basically and about the same size. So I filled the instructions rebooted it and held the R down until a menu appeared asking me which volume to boot up from & I apparently selected the incorrect one cuz all I’m getting is this file folder with a question mark whenever it tries booting.

I’ve tried holding the button down at the blinking question mark folder and pressing R then I tried holding Commamd +R with no luck. Occasionally it’ll boot up to the internet download option for the OS but then fails about 30 mins into it I’m guessing cuz of

my terrible internet connection but its anyone’s guess rt now why it’s failing the internet attempt. It’s possibly important to note that at one point I’ve seen 2 diff type of menus for the internet download and cuz this is due to hacking problems that I’m not sure how that all works here I wanted to say something about the diff in menu styles if u will cuz the 1st time I tried I got an actual globe telling me it’s downloading the OS & that it may take a while. Then at some point after failing it showed a globe without the progress bar underneath it showing the current stage it’s at downloading this with the same “this may take a while message”. And now when I power it off and hold R or the Cmd plus R combo it continues to just take me to the blinking file folder like u see in windows explorer icons with a big question mark.

I believe I need to simply select the other avail volume for it to try to boot up from but I’m not even sure this has the OS just cuz maybe that’s why the guy didn’t erase it when he sold it to me a while back idk. But anyway if u could help me out here a little with some guideance to get it back to a fresh state install with I believe Catalina was the latest I had on it which was a feq upgrade about a year ago. I did the upgrade from the apple dot com website successfully. Now I’m sitting here with a dead laptop cuz it got hacked pretty severely and not even sure what got screwed up from viruses fake screen menus etc I’ve seen it all on all my devices that all connect thru my one phones mobile hotspot where this is all coming from I suspect from my home aka mobile carrier network or employees there and can’t get rid of this crap but it’s spread to every device on that mobile hotspot connection so I’m just trying to save my MacBook until I can get help from anyone at this stage with the actual hack and understanding about it before reconnecting it or I’ll just sell it if nothing else. Long road I’ve been on and I’m tiring but any help right now would be really appreciated. My tech exp is basically about 10 yrs or so for a state govt help desk which doesn’t exactly work a whole lot attacking or hacking folks but focuses on helping folks hence the actual name lol so this is just outta my scope but follow instructions technically fairly good fyi if ur willing obv thanks in advance it’s an older mid 2012 MacBook Pro that had Catalina upgraded on it and I’ve got no working cdrom drive at the moment on it