9 to 11 speed partial groupset upgrade? Is it possible?
The Sora front derailleur is not compatible with the front 105 shifter. Shimano changed the actuation ratio (ratio of cable pulled to cage movement) on 11 speed road groups. 

The Sora crank is not compatible with a narrower 11 speed chain. The chainring spacing is optimized for a wider 9 speed chain.

YOu can look up Shimano component compatibility on their product information page.