Just bought a used Trek Farley carbon, need help understanding what I got

After several months searching, I was actually ready to buy a brand new Trek Farley from my local Trek store… but then I came across a deal on a used carbon Trek Farley that I simply couldn’t refuse.

The bike just arrived and, to be honest, I’m still trying to fully understand what I actually bought 😅

From what I know:

• It’s a Trek Farley carbon frame

• I initially thought it could be a 9.8 or 9.9

• But when I checked the serial number on Trek’s website, it only identifies the carbon frame, not a full model

So I’m guessing this might be a custom build from the previous owner?

The bike has been sitting unused for about 2 years, so I’m planning to take it to a Trek dealer for a full service. Does that sound like the right move?

I’d really appreciate your help and opinions on a few things:

Questions:

1.  Based on this info, does it sound like a custom build? Any way to identify the exact model/spec? What you guys think on the equipment it has? 

2.  Is a full service enough after 2 years sitting, or should I be worried about anything specific?

3.  What upgrades would you recommend right away (if any)?

4.  Pedals: what are you guys running on fat bikes. Need to buy because it doesn’t have pedals. Was thinking on Trek Line Elite or Line Pro. 

5.  Tires: mine are slightly narrower than what I wanted, can I run 27.5 x 4.5 on these wheels? Any recommended models for beach riding and MTB?

6.  Anything I should check specifically on a used carbon fat bike?

Any tips, suggestions or things to watch out for are very welcome.

Thanks a lot! Have a great day