The System Reserved partition should not be messed with, it contains the boot manager and boot configuration data. It's also integral to the Bitlocker encryption feature.

The Recovery Partition is pretty much self explanatory, it contain the Windows Recovery Environment (WinRE). If you delete this partition you obviously won't be able to use windows recovery options. You cannot delete this partition under Disk Management but you can using diskpart.exe. Even then, you may have a problem when trying to absorb the unallocated space. If you want to delete this partition, best to use a third party tool such as Aomei Partition Assistant.

Unless you are desperate for additional space on the hard drive, I would suggest leaving both partitions alone.

No, not really. This folder is more tied to the rollback feature. If you have no intention of rolling back to the previous OS, you can safely delete this folder along with the Windows-old folder. I believe they are deleted automatically after one month anyway.