Problems of recreating a chat from the early late 90s to the 2000s

Once many years ago, specifically back in 2017, I wanted to install
a chat on frames to remember my youth. Imagine my surprise when
it turned out that not a single working chat on the frames no longer
existed. All these scripts had shortcomings and errors, since their
developers had not supported them for a long time. So I set about
studying the problem and the result was what you see in this
section.
Here I will briefly describe the problems that I encountered when
creating chats in frames for modern browsers. Thus, here is a simple
description of what I implemented, among other things:
1) Protection from bots without using Captcha;
2) Form autofocus, working in 90% of JS-based browsers;
3) Protection against entering html tags and messages without text
based on JS and PHP;
4) Protection against direct hotlinking of <form input> scripts;
5) Auto-scroll message frame log down without Ajax;
6) Im managed to get rid of the white background every time the
message frame is updated;
7) It was possible to implement a file version of online user
verification;
8) Implemented automatic display of links in the form of links
rather than text;
9) Chats use files, not SQL to work.
These pain points were relevant for all chats of the late 90s
of the 20th century, which did not allow further use of frame
technology in modern browsers. After studying almost 50 chat
scripts of that time, I was able to find out the cause of the
problems and make these changes to my crafts.