The included Magpul trigger guard is polymer.
Daniel Defense does not provide that information. I recommend contacting Daniel Defense in regard to your question with the Daniel Defense AR-15 Lower Receiver Parts Kit.
Yes, it is.
No, it does not. The kit only includes the following: Magpul Enhanced Polymer Trigger Guard, pistol grip screw, pistol grip lock washer, AR-15 pivot pin, bolt catch plunger, bolt catch roll pin, bolt catch spring, buffer retainer pin, buffer retainer spring, disconnector spring, magazine catch spring, magazine release button, two pivot/takedown detent pins, two pivot/takedown detent springs, rear takedown pin, safety detent selector, selector detent spring, trigger guard roll pin, trigger guard set screw, two trigger/hammer pins, bolt catch, hammer spring, magazine catch assembly, safety semi-auto selector, semi-auto disconnector, semi-auto hammer with J-Pin Assembly, semi-auto trigger and trigger spring.