Not feasible. That would entail putting shrapnel into orbit (unlike extant anti-sat weapons which are short-range suborbital), which would mean a full orbital launch for every satellite target orbit. There's hundreds[0] of Starlink orbital groups already, so that'd require hundreds of independent orbital launches in a short timescale—far beyond China's launch capabilities today.
(On general principles, you could argue you'd need 1:1 launch vehicle parity (number, not payload) to defeat a satellite constellation this way. For each satellite launch, you'd need one corresponding anti-satellite launch into that same, newly-defined orbit).
If you make a dense-ish cloud that cuts across the Starlink orbits you'd eventually intersect them all if you could make the artificial debris field last It wouldn't require that many different counter orbiting fields to cover most of the orbits.
Yes but there's so many starlinks that you're going to get lots and lots of collateral damage to sats from allies and enemies alike. It's going to be a huge footgun.
Not much else uses those orbits right now. Other comms satellites and surveillance birds are all higher up. The debris would in theory also clear pretty quickly and should be fairly contained so the cascade of additional damage might be relatively small too. Hard to know that without a huge simulation budget to see how high the shattered satellite bits might get tossed.
For your shrapnel to hit the satellite, it needs to be at the same height and inclination. Otherwise, your shrapnel will likely miss the targets.
Starlink satellites are pretty low and experience a lot of drag, with square-cube law working against you. Your shrapnel's orbit will likely decay pretty rapidly.
