Sierra down loaded by mistake on old mac

[Annie122607]

I have an old mac pro down loaded mac os sierras by mistake from Mojave how to undo . When I turn on it just stays in start mode after I put in pass word the black line is all black and doesn't show the program starting to run. How to get back to el Caption something older? No back up except from time machine last one said aug 2018. Had a cast on hit button by accident.

 

[alex0002]

It isn't very clear what is happening here.
You have an old mac pro, but you were running Mojave - is that correct?

Nothing should happen if you just download Sierra, unless you started the upgrade.
is that what happened?

Can you boot into the recovery partition?

Because if you can, then you should be able to mount or access /Users and backup all the files from your /Users/username directory to a new drive (not the one used for Time Machine). Then if you can either re-install (whatever macOS you actually want), or recover from Time Machine, then it should be possible to get all those files back from that new drive.

I'm assuming you can re-download the applications that you might have installed since your last backup.

But it isn't really clear what OS you were running earlier.
What OS did you want to have running?

Where does Mojave come into this discussion?
Does your old hardware even support Sierra or Mojave?

 

[Annie122607]

It isn't very clear what is happening here.
You have an old mac pro, but you were running Mojave - is that correct?

Nothing should happen if you just download Sierra, unless you started the upgrade.
is that what happened?

Can you boot into the recovery partition?

Because if you can, then you should be able to mount or access /Users and backup all the files from your /Users/username directory to a new drive (not the one used for Time Machine). Then if you can either re-install (whatever macOS you actually want), or recover from Time Machine, then it should be possible to get all those files back from that new drive.

I'm assuming you can re-download the applications that you might have installed since your last backup.

But it isn't really clear what OS you were running earlier.
What OS did you want to have running?

Where does Mojave come into this discussion?
Does your old hardware even support Sierra or Mojave?

[doublepost=1562416546][/doublepost]yes it does support both, actually apple downloaded it for me looking for a problem with deleting old ring tones , these used new phone mac and iPad . actually it was the support team. Sorry this is out of my league i saw both os in download. I was in a cast and hit it by accident. And I hate to saw I don't back up on external drive .
I dont have a problem and don't want to start with one just running slow. Im not equipped with the knowledge of things will have to bring somewhere i guess . Thank you any ways.