car rental pick up in prague drop off in buda or split/dubrovnik possible?

Don't ask us, ask the rental agencies. If they do let you, it sounds very expensive. Considering that they they can't rent a car with foreign license plates in Hungary or Croatia, it would have to be transported back to Czech Republic. Dubrovnik is a long way from the Czech Republic.

There are companies that will allow it but it will cost you a small fortune. When you return the car to another country it has to be taken back to the country where you picked it up...and you foot the bill for that.