If China attacked India, do you think Russia would even give you 3 seconds of support, never mind 3 years? What Russia does for its own interests are no representation of how much support they would give for the interests of others. They're sure as hell not going to send 700,000 troops to get killed and limbless on the India border.
No and neither would the US. Requests for help were made in '62 and were turned down.
That's why India pursued an independent defence policy and an independent nuclear program.
Ukraine very likely wouldn't have been invaded had they kept their nukes and operationalized them instead of listening to the empty promises made by the US & UK that they will hold Russia to its word not to invade on the condition Ukraine give up its nukes.
Budapest Memorandum - Wikipedia
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