You can climb to the top of Mt. Fuji only in summer. During the rest of the year you can climb to the middle by a car.
For details, check out the official website of Mount Fuji in English by Japanese government and Yamanashi/Shizuoka Prefectures: Official Web Site for Mt. Fuji Climbing
Are there any dialects in Japanese?
Yes, many. Here is an example: English: The weather will probably be fine tomorrow. Tokyo: Ashita wa hareru deshou. Northeast: Asuda wa hareppe naa. West: Ashita wa hare ya ne. South: Ashita wa hare de gansu ne.
I want to visit everywhere in Japan. What do you think?
It's not a bad idea to travel all around if you are on a bike. But keep in mind that Japanese culture is rather monolithic because of its long history and small land, and long distance tarnsport can be expensive.
Where in Japan would you recommend visiting?
I'd recommend to visit Tokyo and Kyoto at least. The sea of Okinawa islands is stunningly beautiful, but the sunbeam in summer is dangerously strong. If you want to see snow in winter, Hokkaido region is a safe bet.
How long would you recommend to stay in Tokyo for?
It depends on what you want to see and do. Stay at least for a week if your circumstances allow you to.
Especially interesting areas of Tokyo: Asakusa / Odaiba / Shinjuku / Shibuya / Harajuku / Ueno / Akihabara / Roppongi /
To visit or see: Tokyo Tower / Sky Tree Tower / Tokyo Disney Land&Sea
Experience: Izakaya bar /
Day Trip: Mt. Fuji / Nikko / Kamakura City / Yokohama City / Hakone Hot Springs / Mountains / Odawara Castle