represent the modeling of system requirements through UML use case diagrams. Each diagram should have a full text description that introduces the diagram, its visual elements, the purpose of the diagram, comments on system requirements, etc. these are the requierments:The system must work on older device versions.

Upon registration, downloading a one$-$time key with $3$ one$-$time passwords and entering a phone number must be required.

After $5$ incorrectly entered passwords, the profile must be locked, and unlocking must be awaited through a key or a code sent to the phone number.

The system must work on different devices $-$ laptops, tablets, smartphones.

The system must work on different browsers and operating systems $-$ Android, iOS, GNU$/$Linux$,$ macOS, Microsoft Windows.

The system must only operate in Europe, North and South America.

The system must support languages $-$ English, Bulgarian, Greek, Danish, Estonian, Spanish, Italian, Latvian, Lithuanian, Maltese, German, Dutch, Polish, Portuguese, Romanian, Slovak, Slovenian, Hungarian, Finnish, French, Croatian, Czech, and Swedish.

The system must be able to convert units of measurement as desired $-$ pound, foot, mile, inch, kg$,$ gram.

The system must allow at least $20,000$ users to use it simultaneously.

The system must be able to support at least $100$ million registered users.

Since the system must offer various subscriptions $-$ monthly, yearly, individual, and group, it must also offer an option to change a subscription in case a user decides to switch to a different plan.