Few questions about SharePoint communication site

[Xeryar]

I am new with Sharepoint and trying to build an intranet and knowledge base 
for my team in our new communication site . Can someone please advise if these 
are possibilities. 
1- Can we restrict the search this page box to the page we are on only ?
2- Can we setup a rating system so someone can thumbs up or down 
    on the document level 
3- Is it possible to create a cascade drop down for sub section. It seems like 
    the expand/collapse option in sharepoint only lets you do it at the heading
    level you cant create sub heading and expand those 

[#2]

Hi @Xeryar -

1. Searches in modern SharePoint are contextual, i.e., if I'm in a List or Library, the search will default to the List or Library first. While on a page, not directly in a list/library, the search will default to the current Site first. If you really need a custom search box for the page, I'd suggest using PnP search: Introduction - PnP Modern Search (v4) (microsoft-search.github.io)

2. Ratings can be enabled in each Library Settings

3. Collapsible sections are only by the page headers, no option out of the box for a second level of collapse/expand

Hope that helps!