Hide Header from a single page. – Theme 2020

First, I have searched many forums and videos (including this one), tried all options I found, but nothing is working.

I want to find the CSS code (or other option) to remove the header (maybe footer too) from a single page in my published site.

Below you will find all the options I have found, and tried, that have not worked.

I have cleared browser cache after every attempt.

I am adding the codes to Custom Theme CSS

When using the following code it does remove the header from the main page so something is working, and it works instantly.

.page .site-header {
display: none;
}

However the following (all suggestions on here) are not working. Please help.

.page-id-245 .header-wrap .col-md-8 {
display: none;
}

.pageid-245 .header-wrap .col-md-8 {
display: none;
}

.page-id-245 .top_bar {
display: none;
}

.pageid-245 .top_bar {
display: none;
}

.singular-page-245 .site-header {
display: none;
}

.singularpage-245 .site-header {
display: none;
}

.page-id-245 .site-header {
display: none;
}

.pageid-245 .site-header {
display: none;
}