Help with 15 year old MacBook Pro

help with 15 year old MacBook Pro.

I have an almost 15 year old MacBookpro. At some point, I updated its RAM.

Then at some point it was not able to retain charge so I could not use it without plugging in.

I did not use it for many years after that. Finally I decided to give it away and in my zeal to format it and remove my files, I think I completely deleted OS or did something very wrong.

Right now, I can turn it on, connect to wifi account, update time and date using command prompt.

But it keeps giving pop up window - restore from back up, re-install OS, disk utility.

But none of the options are working. There is no back up disk, I am not able to connect to apple and re-install OS, selecting disk utility gives me blank window because there is no recovery drive.

I am not able to do anything after I turn it on.

Is there anything I can do at this point?

I want to at least make it workable before giving to someone. I hate to just throw it away if there is a chance to salvage it.

If I cant install anything, is there a way to make sure all my data has been erased from the hard disk?

Thank you all for your time and help.