What are the restrictions for inserting data in "User tag 1" and "User tag 2" fields, like maximum number of characters, special characters and spaces?
Controller 7.80 or later
The user tags info is recorded in UIM DB, in CM_NIMBUS_ROBOT table, inside the "user_tag_1" and "user_tag_2" columns.
These fields are defined as VARCHAR(256). So, they can accept alphanumeric characters, with a limit of 256 characters.