Hi digimigia,
Thanks for reaching to us and take our apologies for the long delay in answering.
1. Header and Footer
In order to remove header and footer from specific page, you can use with page ID. Please add the following Custom CSS code to Theme Settings > Custom CSS > Global Custom CSS:
.single-product.postid-xxx header,
.single-product.postid-xxx footer{
display: none;
}
xxx: ID of page, which can be found in the address bar https://prnt.sc/HDZ_1RVDRAcs
2. Related Products
There is an option to hide Related Products via Product Settings > General tab https://prnt.sc/koOy_qj4PX-m
Regards,