I'm trying to re-render my animation, and by that I mean I'm trying to fix a certain area of frames that have light and grain issues, so that when I want to render the rest of the frames again I could just slide the start frame to where I fixed all my other frames, but whenever I hit the animation button, it says "sequence render," which already renders the unfixed frames from my previous render. SO my big question is, how do I stop the sequencing render and render a set of new frames with the same animation? Mind you that I also want to render each and every frame on a .png file within a separate folder.
First, you did the right thing by rendering into an image sequence. Never render animations directly as video.
Delete (or move to a different folder) the frames that need to be re-rendered. Then on the output settings uncheck the "overwrite option"
Then re-render as usual wiht CtrlF12. Blender will just render the missing frames and leave the others untouched.
If you have any strips on the VSE (video sequence editor) uncheck the Sequencer box of the postprocessing section of the properties window.