Always backup theme files before making code changes.
In theme.liquid add the following before the opening tag and tailor the placeholders ‘-handle’ to need.
{%- if template == 'index' or page.handle == 'page-handle' or product.handle == 'product-handle' or collection.handle == 'collection-handle' -%}
{%- comment - %} DISABLE SCROLLING {%- endcomment -%}
{%- endif -%}
Advanced but cleaner alternative - if you have a OS2.0 theme that lets you add a custom liquid block to the entire site do that instead of modifying theme.liquid directly, or add the CSS as custom-html blocks directly to a the homepage and for your other page give it an alternative template again giving it the CSS in an custom-html block.