2A. Main take home is DSI intake. You can't just plug it into any airframe. Once a jet fighter
decides to incorporate DSI intake, the entire stealth characteristics must be recalculated with a
supercomputer, which means a different resulting airframe design altogether.
Image below F-22 without DSI intake:
2B. Simply check out the slick beautiful non-gapped DSI intake of the J-20 (below):
4. Radar range (microwave emissions) of the J-20 (4th from top) vs F-22 (second bottom):
Anyways, none of it really matters. Since J-20 just passed design and prototype phases into early production model, the Chinese already started working on a 6th gen stealth fighter that will be much better than their own 5th gen J-20!
P.S: The American F-35 is a flying pig as shown above!
J-20 cockpit (yellow color of these birds is the primer that helps the paint [applied later] to stick. The radar absorbing layer already "pre-baked" in beneath the primer):
Little oval capsule beneath J-20's belly is an emitter to help keep track of the planes during flight testing (otherwise these stealthy planes would be invisible to radar).