To reach Besançon

Besançon can be reached easily from Paris. From Roissy Charles de Gaulle airport, which is connected to railways, there is one direct connection but only once a day in the evening.

Cheaper and faster:

19h58 CHARLES DE GAULLE 2 TGV

22h31 BESANCON FRANCHE COMTE TGV
But you have other possibilities through Lyon at any time.

Alternatively, you can go to Paris-Gare de Lyon railways station (with RER local trains), where you can find frequent trains from Paris to Besançon. It is better to arrive in Besançon Viotte rather than Besançon Franche Comté TGV, because this is closer to the town center, but shuttles exist between both Besançon stations. From the other regional airports (Basel or Lyon, connections are also possible). https://www.oui.sncf/billet-train

From Genova, it is more difficult because you must cross the Alps and a foreign country, but if you decided so, you should rent a car.