Recovery mode not working

I have a mid-2011 iMac 21.5" running High Sierra.

When the OS started acting weird, running slow, and not loading thumbnails for photos and screenshots, I decided to reinstall the OS, but Command + R does not work to open recovery mode. Option key does not open the Utilities either. Option + Command + R did open Internet recovery, but after the spinning globe progress bar finished, I got only the Apple logo for 24 hours.

So I reinstalled High Sierra from the App Store, and it did run faster and fix the thumbnails. But still no access to recovery mode for the future.

In Terminal I ran diskutil apfs list and got "No APFS Containers found."

Then I ran diskutil list and got

/dev/disk0 (internal, physical):

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme *250.1 GB disk0

1: EFI EFI 209.7 MB disk0s1

2: Apple_HFS Untitled 249.2 GB disk0s2

3: Apple_Boot Recovery HD 650.0 MB disk0s3

So apparently there is a Recovery HD volume, but it's not APFS?

In Disk Utility, no Recovery HD volume appears.

Anyone have any ideas how I can repair this problem and restore access to recovery mode?

Thank you