I just bought my first home it was built in 1902 and we wanted to remove the old carpet to refinish the orginal hardwoods. So the first issue I encountered was glue. There was lots of glue! I used some adhesive remove which removed most of it, then kept scrapping a majority of it away.

Once done we decided to rent a orbital sander and bought loads of sheets in 36grit which is the lowest they sell with the machine. The paper we noticed would only do about 5sqft at a time before we were gumming up.

So a buddy recommend we get a drum sander which was amazing. It removed pretty much everything. But my only issue im having is some of the floor is not level and the drum sander could not reach it. Basically we have darker spots still. I read online that I should try going at a 45degree angle to help level them out? Or should I just get a hand sander and sand down the darker areas?

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Yes diagonally sanding will help get the floor flat. This method cuts faster than going with the grain. With an old floor I would not sand diagonally after it has been sanded to flat. Any lower or dark areas may be scraped to get the surface smooth and take off anything that's foreign. You just want to get a smooth floor that can be cleaned and get a finish that will not wear through to bare wood right away. Scrape and hand sand will do most times. An edger will get a small area smooth but not always flat. Don't take off wood that will make the floor surface wear out and need to be replaced, mostly from splintering as the top of the groove gets thin. Some stains can be a quarter inch deep into the surface.
Looks like you have old growth flooring which is getting more and more scarce.
The field of what looks like pine can cost more than the oak in the borders.

Thanks for your response. My second issue I'm having is matching my floors downstairs to the upstairs. My upstairs have this orange warm feel to them. In the picture i tried Shellac amber on the right then oil based poly in the middle and Clear shellac on the left side. None seem to match.

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I've heard that you can buy tint at Wood craft stores. you may find one that is close.