I’m surprised you couldn’t find it, it’s covered in a lot of blog articles.
In order for the first two methods to work you must’ve backed up your iPhone/iPad using iTunes on the laptop. They won’t work if your back ups are in iCloud.
But as long as your previous backup was on your computer, there’s a copy of the previous version of most apps on your computer. There are a few that won’t work because they will automatically update themselves or because there’s some data that’s kept in a cloud. But it will usually work.
So You know there’s a copy of the app on your computer, it’s just a matter of deciding how to get at it. This is where the blog articles come in because there are least two different ways to do this, and I think maybe three. Here are some examples.
If you get a “subscribe to blog” pop up on The first one and you don’t see a way to close it, just back off the page and come back to it it should be gone.
Also, note that you only want to use blog articles that are fairly recent, because this method does change occasionally.
The following blog article 1st covers the synch method, which is easier but you have to have everything set up just right, and then the trash method, but it doesn’t have as much detail as the previous one.
And a third method which is really long and complicated and you should only consider if you don’t have a copy on your own computer.
And as others have said, you can also just postpone the update until you’re pretty sure it’s OK.