Premium Accounts Outlook and Android
I plan to use Todoist on both my Android device and sync it to outlook. If i pay for premium service, do I have to pay two premium service fees? One fee for Android and one for Outlook?
You don't have to pay multiple times. When you upgrade to Todoist Premium - your account becomes "Premium" and you can access all Premium features on all platforms - Outlook, desktop apps, web-app, mobile apps etc.
Does the same apply if I only paid for 1 month?
Yes, every single payment causes your Todoist account to upgrade and not a certain app. That is - if you upgrade your account, you can access it through all apps, plugins etc. the apps themselves can handle both types of accounts - free and Premium so it's not a "per app" payment, but "per account".