Yes, this bike is equipped with ISCG-05 tabs for easy chainguide mounting. Most chainguides on the market that are made for this standard should work.

No, this bike is not compatible with front derailleurs.  

We always recommend the stock shock, as we've spent a lot of time tuning for each particular frame. But if you must, these are the specifics you need to keep in mind:
- 210x50 Metric shock
- 30x8mm rear hardware (bearing compatible)
- 20x8 front hardware

A coil shock will fit in the Furtado, but we generally recommend an air shock as they are more progressive and tuneable.

There's a "flip chip" on the link where the shock mounts. Just remove the lower shock bolt and flip the chips to the setting you desire

This bike uses a 180mm post mount. You cannot run a smaller rotor than that. If using 180mm rotor, your caliper will bolt straight to the mount. For 200 or 203 rotors you will need a 20mm or 23mm Post Mount adapter

The Furtado will fit up to 27.5x2.8" tires, but we sell it in two configurations:
"Normal" configuration comes with 2.3" tires on 27mm rims. This setup will offer the most precise handling, and is your best bet if you prioritize responsiveness and low rolling resistance. The rims will work well with tires up to 2.5" wide.
"Plus" configuration comes with 2.6" tires front and rear, on 35-37mm rims (depending on kit). These tires offer a good combination of grip/cushion without giving up too much in the way of support and precision. The rims will also work excellently with 2.8" tires if you're after the true rock-crawling Plus experience.  

Thanks to the flip-chip on the link, you can adjust the bb height to account for the different tire diameters. You can achieve the same bb height with the plus configuration as you do with the standard one.