Can I use Fotocal without ever paying?
Yes, for as long as you like. The free plan is 2 photo scans and 1 voice log a day, unlimited barcode scans, unlimited Coach Kal, the diary, weight, water, steps, notes, the Progress tab and the weekly report's free cards. It never expires and never asks for a card.
Which plan has the free trial?
Every paid plan. Each one starts with 5 days of Premium at no charge, once per Google Play account. On day six Google Play charges the price of the plan you chose.
What exactly happens on day six?
If you have not cancelled, Google Play charges the plan you chose, €6.99 for the month or €34.99 for the year, and the plan begins. If you cancelled at any point in the five days, nothing is charged and you keep Premium until the trial ends. Two to three days before the charge the app sends a single reminder naming the date and the amount, unless you have switched that reminder off in Settings.
Do both plans unlock the same things?
Yes. There is one Premium. The only differences are the price and how often it renews.
Can I switch from one plan to another?
Cancel the plan you have in Google Play, let it run to the end of what you paid for, then subscribe to another one from inside the app. You are never charged for both at once.
Are the prices the same everywhere?
The prices here are the euro list prices, VAT included. Google Play may show a different amount in another country or currency, and the amount it shows before you confirm is the one you pay.