Hi, thanks for your replies and your interest.
Note that if you have no problem with security about passwords and logins entered in any computer used by many people, it does't mean that nobody should have security problems like you.
Maybe you all use Mac. Does someone use Windows?
Anyway, my first post was a question about the existence of an app for iPhone (or a feature of the last iOS) that allows user to use pc (any pc, not only Mac) keyboard, big screen and mouse to interact with his iPhone's apps through a pc web browser and without entering of any ID or password, in the same way the app WhatsApp (it is an example app, maybe there are similar apps) allows user to scan a qrcode to use WhatsaApp in a web browser page,without entering any phone number.
Conclusion: based on yours replies, this feature/app doesn't exist. The only way is to use icloud.com in any pc web browser and enter Apple ID and password in order to use only Apple pre-installed apps like Mail or Remainder with pc, no way to use other apps installed in iPhone. That way is the same way user enters his password in web browser page for any email client if he wants to read his email in a host pc, like we do since about 1995.
Cheers
Apple has a very powerful but tight ecosystem. Outside of apple products (Microsoft) their cloud based ecosystem is broken. I prefer iOS because I prefer MacOS and I prefer MacOS because I prefer iOS. Without their tight ecosystem integrations I would be an Android user no doubt.
With MacOS, an iPhone and iCloud enabled you have access to most of the stock apps via native MacOS programs. Reminders, phone, messages, notes, maps, photos, pages, numbers, Calendar, etc etc etc are all MacOS programs that sync with your iOS device. Example, type something in the Notes program on your Mac and its in your Note.app on your iPhone. Open directions in the MacOS Maps program and send it to your iPhone. Get a Phone call on your iPhone and you can answer it on your Mac.
But more to the point of your question.
With an AppleTV you can AirPlay mirror (screen mirror) you iOS device screen to a big screen. iOS also has bluetooth keyboard support, so if you want to hammer out some emails, documents or whatever on the big screen via your iPhone with a keyboard that is definitely possible.
You can also get an AV adaptor to plug directly into your big screen as well. However you can probably pick up an AppleTV 3 cheap enough that it outweighs the cost of an adapter.
HOWEVER iOS does not support mice/trackpads. This is intentional since the touch and gesture based interface of iOS doesn't convert very well to mouse/trackpads. Android is a prime example, even some of the oldest Android devices supported USB hosting (plug in a mouse and a mouse cursor would pop up on screen) however the fun stopped there since you would need to emulate touch based movements with a mouse. Even in times like these where many people feel the level of polish of Apple products is waning, just adding mouse support would be a no-go without a specific overhaul for it. And by overhaul I mean iOS would need to shift into a "desktop" or "mouse mode" or something for right click support, double click support, dragging (without a long press), etc etc.
Again your options are somewhat limited with Windows and Linux. In lieu of sounding like a fanboy you sound like someone that might appreciate a Mac btw. I run Windows 10 and MacOS side by side but only use Windows when I absolutely have too (generally machine firmware updating via proprietary software).