Yes you can travel alone but the streets are not well signature and the public transport outside of Nosy Be is quite a challenge. I would suggest to take a good tourguide on your hand who speaks your language so you feel comfortable.
The signalisation is almost not existing and Internet is not everywhere.
Best is to buy a SIM Card from Telma or Orange and buy a plan for 25.000 Ariary
Most Shop`s taking the local currency Ariary. You can bring EURO to exchange it here in Madagascar little notes are more welcome than the big one in the exchange offices and banks. Would be good to check if you can pay the hotel with the credit card. Cash drawer only existing on touristic areas Visa is working everywhere Mastercard sometimes.
Yes the best is to do the Visa on Madagascars Airport.
The 15-day tourist visa costs 10 Euros.
The 30-day tourist visa costs 37 Euros.
The 45-day tourist visa costs 45 Euros.
March to November is the best time from December till February is raining Season.
Miskito Spray, Shorts with light Material, open Shoes, Flip Flop, Sun cream, enough EUR, first AID kit, Aspirin, Imodium, Fenistil, Malariaprohylaxe, Filter Bottle like Katadyn (the tap water is not drinkable but you can buy water at the supermarket)
All year between 28°-33° degrees, attention capital city of the main island can be much colder. Depends on where you plan to travel in Madagascar check first the tempretaure befor you pack your suitcase.
It is not an obligation to enter Madagascar, but the doctors recommend it.