Usually the last or the penultimate weekend of every September take place the Hellenic annual climbing meeting which is organised by the Hellenic Federation of Mountaineering & Climbing.
Meeting point is the camping "Vrachos" at Kastraki village which is also the climbers' meeting point generally.
The Larissa airport is military and there are no flights for this destination. Most probably there are some exceptions in the summer for charter flights in the airport of Nea Agchialos, near Larissa, which is also a military airport.
Stutte & Hasse have released the 3rd edition of their guide. There is also a book called "Meteora - A Landscape To Be Experienced" from the same authors.
Although not a law, it is common practice to open routes from the ground up. Bolting however is accepted (and necessary) because this type of rock rarely takes natural pro. Adding bolts to an existing route is discouraged.