Re: non stealthy undercarriage?
It's the straight edges on the doors. When closed, they leave a straight seam which acts as a radar reflector. If you look at the pupose-designed stealth aircraft, the external doors (undercart, bomb bays et. al.) all have wiggly edges to avoid this effect.
This is most obvious on the F-117, the original Stealth Fighter, where the gear doors have an edge like pinking shears due to its "triangles only" design, which arises from modelling radar reflection characteristics using '70s vintage computers which didn't have the horsepower to do this for curved shapes.