No card to start. No trial clock on the core system. Pro is optional.
Buying Pro for someone else? Gifting is not automated yet — email bijoy@serene-designs.com and it will be set up on their account by hand, usually the same day.
No. There is no countdown on the free tier and nothing in it expires. The optional 14-day Pro trial is separate and entirely opt-in — you choose to start it, and when it ends you drop back to free rather than losing your account.
No. Signing up needs an email and nothing else. A card is only ever involved if you decide to buy Pro.
Subscriptions are non-refundable. That is exactly why the free tier is permanent and the trial requires no card — you can see the entire product working on your own data before any money is involved. You can cancel at any time and keep Pro until the period you paid for runs out.
Nothing is deleted. Your account drops back to the free tier and everything you logged stays exactly where it is — the Pro views simply stop being available until you upgrade again. Your history is never held hostage.
It is a web app, so it runs in the browser with nothing to install. You can add it to your phone's home screen and it will open fullscreen like an installed app, but it is not distributed through the App Store or Play Store.
Not at the moment. If that changes it will be announced to people already using Sovereign first.