Other than the difference between сАмого и самогО in spoken language, no, Russians don't have a habbit of putting accents on vowels, unlike Italians.

You can tell the difference between the meanings of сАмого as "the most" and "the very" if you ask yourself: can this adjective be the "most" (or least, or more, or less)? I think these are called качественные прилагательные in Russian. If "most" fits, then it's "most". If it doesn't, it's "very".

So, since the window cannot be the "most open", and the sea, except by a stretch of poetic imagination, cannnot be the "bluest", you know it means "right by the x", or "by the very x".

In reality, unless you are reading Pushkin, you don't run the risk of stumbling upon the "у самого такого-то того-то". It will be simply "у самого окна", which you will immediately recognize as "right by the window".