Box 1: Last Modified -
The Last-Modified response HTTP header contains a date and time when the origin server believes the resource was last modified. It is used as a validator to determine if the resource is the same as the previously stored one. Less accurate than an ETag header, it is a fallback mechanism.
Box 2: If-Modified-Since -
Conditional Header If-Modified-Since:
A DateTime value. Specify this header to perform the operation only if the resource has been modified since the specified time.
Incorrect:
Not ETag/If-Match -
Conditional Header If-Match:
An ETag value. Specify this header to perform the operation only if the resource's ETag matches the value specified. For versions 2011-08-18 and newer, the
ETag can be specified in quotes.
Reference:
https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Last-Modified
https://docs.microsoft.com/en-us/rest/api/storageservices/specifying-conditional-headers-for-blob-service-operations
