Hi ihavequestions, The answer to your question is 'yes', the aircraft will continue with the mission and end at the programmed point in the programmed manner ie hover or land. The reason that the aircraft completes the mission is that the whole programmed mission is uploaded from the tablet to the aircraft via the controller just before take off.
A tip I will add is to programme the missions to always end near the start point even if this is not neccessary for the purpose of the mission. I always take manual control at the end of the mission and hand catch.
When the loss of signal is only temporary, for example if the aircraft flew behind tall trees or buildings but then re-immerged then the controller will reconnect. Technically you don't absolutely need to have the controller connected during the flight but it is of course highly advisable so that you can flick the switch into Sport mode temporarily to halt the mission and regain direct control of the aircraft. Remember that although Litchi is a very capable system YOU remain responsible for the safety of the flight.
Loss of GPS only happens when there are issues with the GPS receiver in the aircraft or when the view of the sky is obscured, for example if you were attempting to fly along trails in a forest. (I have seen videos of people attempting to fly through tunnels and being surprised by loss of GPS!)
All the best, Martin