Oracle Database Discussions

I am trying to figure out whether I can query the Oracle meta-data to look for:
a) comments on tables and fields matching a certain text pattern. If possible I would LIKE the text pattern matching not to be case-sensitive. Am I looking within the right meta tables?

SQL> desc all_col_comments
Name Null? Type
----------------------------------------- -------- ----------------------------
OWNER NOT NULL VARCHAR2(30)
TABLE_NAME NOT NULL VARCHAR2(30)
COLUMN_NAME NOT NULL VARCHAR2(30)
COMMENTS VARCHAR2(4000)

SQL> desc user_tab_comments
Name Null? Type
----------------------------------------- -------- ----------------------------
TABLE_NAME NOT NULL VARCHAR2(30)
TABLE_TYPE VARCHAR2(11)
COMMENTS VARCHAR2(4000)

See http://asktom.oracle.com/pls/apex/f?p=100:11:0::::P11_QUESTION_ID:233014204543.

b) I was trying to look up a text named 'PKa200030' which showed up within an application upon which we are developing. The application uses Oracle 11g Enterprise Edition. However, I could not find the name anywhere when querying all_constraints, so I am not sure how to trace back the table name / package name, by knowing what seems to be a primary key constraints, any ideas please?

select c.table_name,c.constraint_name, --c.r_constraint_name,
cc.table_name
from all_constraints c
inner join all_constraints cc on c.r_constraint_name = cc.constraint_name

See http://stackoverflow.com/questions/3210743/viewing-oracles-metadata-about-primary-foreign-key-constraints.

c) I am not sure whether it is possible to draw a database entity model, perhaps using software, assuming that the primary/foreign keys have been already defined within Oracle 11g. Is software available to do this?