Protect a text with a password: it's encrypted with AES-256-GCM (key derived via PBKDF2) right in your browser and turned into a single string you can store or send. Decrypting needs only the string and the password.
No. All cryptography runs locally in your browser via the Web Crypto API.
The text is unrecoverable — that's the point of strong encryption. There is no reset.
AES-256-GCM with a key stretched by PBKDF2 (150,000 iterations) — the same building blocks used by password managers.