Soviet pilots flew MiG 15's against American planes in Korea, and MiG-21's in Vietnam. Soviet missile crews shot SA-2 missiles at US planes all the time. Every war we have fought in the past 70 years has been against USSR/Russian weapons, and Russia has had no qualms whatsoever about arming the enemies of the US.
We can give Ukraine whatever the hell we want, and if they use it to hit inside Russia that's just fine. If US pilots fly "Ukrainian" F-16's that would be fine too.
We will not transfer a missile with a range greater than 300km. That's the MCTR (an actual agreement) limit, and we adhere to that. Anything under 300 km is not restricted.
Russians are firing missiles at Ukrainian cities every day, usually from well inside Russian territory. Russia attacked Ukraine, and Ukraine is completely justified to attack any militarily significant target inside Russia.
Russians should hear "boom" every night, for as long as there are Russian troops inside Ukraine.