Hibiscus (rose of Sharon?)
Reading your article on when to prune the Hibiscus was a lot different then I was told. So your article
says to do it just as the plant begins to bud in the springtime. I was told to prune my plant in March when it was dormant. I pruned mine (zone 5) in March/early April and it looked like it was budding, then it stopped and now it looks dead. It seems I killed it, as it never bloomed this summer after years of beautiful blooms.
I saved seeds from it so I might try growing another one. So basically wait for the plant to start to blooming and then prune it back? This had beautiful flowers on it each year but grew to an out of control bush. I tried to tame it but looks like I killed it instead.
In many years, trimming when you did would not be harmful, but there may well have been a cold snap after you trimmed. However, your bush is probably not dead, just frightened. In other words, stress of cold and stress of early trimming was a bit too much, and it might take a year or two to recover.
The recommended method for propagation is by cuttings. You can start from seeds also, but most of the plants sold in nurseries are hybrids, and have been developed to inhibit propagation from seed (so the dropped seeds won't result in thousands of unwanted plants.)
You can certainly try to start the seeds if you want, but my information says the seeds only last for a year,and they need to be kept refrigerated if they're not sown immediately upon ripening.
If you want to try starting cuttings, this article will be helpful: https://www.gardeningknowhow.com/garden-how-to/projects/rooting-plant-cuttings.htm