As per documentation(or should i say popular belief ... as i did not find exact documentation link) 18 digits are case insensitive and 15 digit ids are case sensitive.
In fact many site blogs says that 18 digits was invented to ignore case of characters in id field.
When I tested it in developer console and workbench it did not work as expected.
For ex, my account id is '0019000001AWn2o'. In 18 digit format it is '0019000001AWn2oAAD'
Now, if we change case of any characters in 18 digit id then also system should work. (At least that is what interpretation about case insensitive ID)
But to my surprise non of following ids work in SOQL ,URL or from API
So, what it seems like the popular belief is wrong that 18 digits are case insensitive. But last 3 digit just act as check sum for validation.
I know that we can decode the 18 digit id and get the original 15 digit id but i was expecting that platform should have handle it when I pass 18 digit id.
Am i missing something here?