Does Devourer proc lifestealing twice?

it basically procs a second auto attack that deals no damage itself. so technically yes, it procs lifesteal, but since the second attack deals 0 damage, youre also not getting any health. it might even be able to crit for 2.5 * 0 damage.

since they overbuffed bork, you will however lifesteal from the second bork passive.

Phantom hit only applies on hit effects. so it's basically treated as an auto attack with 0 AD. Technically yes, but it would have no effect.

certain on hit effects will apply Life steal however, such as BotRK and Hydra, and those would be affected twice.

It procs life-steal, but because you do 0 auto-attack damage the second proc also heals you for 0.