Which Tern is suitable for a beginner commuter? I live in Dublin, CA. I have a 5 miles commute each way from my house to my office. There will an upward climb on the way back home.

Google map with biking route

I am a beginner when it comes to biking. I haven't biked for years since I was a kid. Previously I lived in a city where transport is very convenient so there's no need for a bike commute. I just relocated to Dublin, CA for studies and work, it's a suburban area with swathes of land so I have to bike to get from point A to point B. I have to commute to Stanford via trains/bus as well, so it's helpful to have a bike that can fold.

I'm looking into buying a Tern. Brompton is too expensive; I don't know how to appreciate the higher-end folding bikes since I haven't rode a bike in years. I thought I'd start off small with an affordable but sturdy foldie like Tern. 

I'm looking into two options: Tern Link Uno or Tern Link D8. Link Uno is cheaper as it is single-speed, and it looks aesthetically pleasing as well. I'm not sure whether I can handle multiple gears since as I said, I haven't cycled in a long long time. However, judging from the bike path, as you can see on the Google Map, there will be an uphill climb near to the end of my journey home. I'm not sure such a climb is considered steep; you should know that I have no prior experience biking in such a suburban place (I lived in a city all my life). Hence I seek your expertise on this matter. Will that warrant for a Link D8 instead? It has multiple gears so that I guess it can take care of the uphill ascent. 

Hills aside, which bike do you think is more suitable for a complete beginner? I'm 6'1" tall, 187 lbs, in generally good shape.
If you can afford gears, buy them. Having an uphill section at the end you will want to shift up in order to make it easier. Going the oposite direction you will also like the ability to go to a smaller gear to get a little more speed downhill. Looking at the pictures linked, it seemed the that the single speed have a rather small rear cog compared to the geared bike. 

If you can't handle shifting rapidly you can always leave it your geared bike in one speed, but at least you'll have the option of chaing it for those morning where you feel weaker or have less energy.