How can I revert back to Mojave iOS

sanbnda wrote:

... How can I revert back to the previous iOS?

Revert your Mac to a previous macOS version - Apple Support

Or, you can upgrade the Adobe and MS apps you require. They will want money.

Or, you can find alternatives to them. There are many such alternatives, some of which are free.

You can restore from your TIme Machine backup:

Restore your Mac from a backup - Apple Support

If you have no backup, then you'll need to erase the disk and reinstall. This will wipe all your data.