The page isn't waiting for the resources to render, browsers generally always render HTML as soon as they have it available. However, the CSS and JS files are likely being sent before the generic HTML for the page, as web designers don't generally like their page to go through multi-step formatting processes while the CSS page loads in, nor do most users. You're likely getting almost none of the HTML until after the CSS or JS loads. Presumably, if you have full control of the browser's functionality, you may be able to tell it to skip these or save the address to load in later? I wouldn't recommend this behavior though, as it could break a lot of functionality, especially with JS.
If images are missing, they should show the alt text. If they're loading, they may not. Again, with full control of the browser, I don't see why this should be a problem for you.
There is no 'generic' CSS. CSS rules are largely customized based on classes and identities defined by the author. More modern webpages which make use of newer HTML5 elements have more semantic information available to guide display without a stylesheet. Short of this, you need the accompanying stylesheet for proper display. You could attempt to guess or reengineer, but the vast majority of the time this will fail, as there was little to no convention prior to HTML5 bringing in more semantic elements.