Upvote:1
I took the bus and before that asked some questions via e-mail to the company, so I can give a partial answer how it goes, in case someone is interested.
I pre-booked the tickets on internet (you have to put the date and also with which plane you are arriving, and supposedly the bus will wait for you). When I arrived at the airport (which is quite small) I was the last in the queue for getting through immigration/customs (the queue was moving very slowly too) and was also questioned quite long, so I think I arrived later than the scheduled time in the end, but the bus did not go away. At the front desk of GeorgianBus, I showed them my prebooked printed ticket, and they gave me a card format ticket instead, with which I could board the bus.
So here is a partial answer to my questions based on that:
Question #2: They told me via e-mail that buses are flight connected and wait for the passengers, also that they have "unlimited" seats (I guess that means that they check how many passengers are on the flight and send as many buses). In my experience, it did not seem to matter much that I had pre-booked the tickets either. About flexible, they told me that you can change the departure time within one year if you can't use the ticket. So if you book online, I would definitely recommend asking for flexible option, for just 1 GER more.
Question #3: Geosim and Georfund are for Georgian citizens going abroad.