Servicing full suspension bike after long period of not being used
I would service the suspension. If the seals have dried out (a safe bet), and you go on a dusty (or muddy) trail ride, it seems inevitable that material will make it through the seals, damaging your stanchions, among other things.

After a friend passed away, I was tasked with selling his old bikes. His FS bike had be sitting idle for about four years. I cycled the suspension and everything seemed fine. But the next morning, all of the shock's oil was sitting in a pool in my garage.

However, if you inspect the seals and it appears that they're still in good condition and you're only going to stroll through the neighborhood, it might be fine.

The brakes might be fine, but I would definitely verify their function around the neighborhood a few days before I took it out on the trail. And then the again the day after that to make sure that all of their seals haven't failed catastrophically like my friend's shock seals.