They have not, I've been flying this route since the CO days around 2009 and for all the years its been CO/UA 48/49, UA829 and 830 doesn't sit with me, so Im sticking to UA48/49 and 82/83. It will be back to UA48/49 in the summer.
Mumbai's flight wouldn't be feasible for too long nonstop without Russia. On the way in, you'll scratch a small part of Russia as we usually fly over Scandinavia on the way in. However, even though GCmap shows the route using a small part of Russia, this is pretty much never the total route taken on the way back to the US to make the journey feasible because the route goes deep into Russia to take a more polar route due to those strong Atlantic jet streams. That alone would make the route hard to operate without a fuel stop somewhere as the route did do with Bangor in the few days leading up to the cancellation of the route.
Cutting the rest of your quote for brevity, but to echo earlier points this is not SOP, but flights in and out of India right now on UA are so packed from a mix of weight restrictions and people from canceled flights trying to be rebooked and I guess apparently capacity constraints for booking partner flights they don't have a feasible alternative for now.
Up to WineCountryUA. Would be cool for sure, although with those BOM flights cancelled until the summer/monsoon, Im not sure there's much a discussion, but nevertheless yes I would have a fun time with a thread like that. It's almost like a little family on those routes too I think I've actually ran into a few people who we all recognized each other over the years making the commute on that plane
Yes DEL will be shorter in almost all circumstances flying anywhere compared to Mumbai purely due to latitude differences. And the difference would be even greater if Delhi didn't sit so close to the Himalayas making planes go around.