thanks, I will try that

Abort abort. I tried it and it failed. I assigned nil to <backspace> but characters were still vanishing. Maybe I will be forced to create mu custom backspace handler...

Thanks. Sounds like good idea. I will do that. My use case is that I want to hide some portion of buffer using overlay display property and I dont want that hidden part of buffer to be editable. It would be best to have completely immutable part of buffer, but killing <backspace> will be enough for me.

I consider this solution to be ugly hack.

Minibuffer line looks like it should work, but I dont tried it in current phase because I consider it somewhat "hacky". Advices are not optimal solution, but very explicit, so I will probably not forget how it works in future. I will try minibuffer line and write how it goes.

Not works for yes-or-no-p.

For example, calling yes-or-no-p. Even hooks from phils doesnt work, only way which I see is to use awful lot of advices.