Ok, starting from the top :-
11 - Williamstown, 3rd duplex, issued around 1894. Not rated
The 2nd stamp is actually not 15, but MC over 15, which is 1115. When they reached numbers starting at 1000, they decided to change the format to half Roman numeral and half normal - so 1001 was M1, 1360 would be MCCC over 60 etc. The Roman numeral part represented the thousand and hundreds, then underneath would be the tens in normal numbers. Except for the 1000 series where the number was beside the M. For the Romans, the bars beside the numerals were horizontal. They later abandoned this idea, so you will sometimes see issues that had a Roman with a reissued normal numeral. Anything after 1600 was always just normal numerals, they'd decided by then to change. So your 1115 is Trafalgar, not rated.
355 - Warracknabeal. Unfortunately not the rare one. Type 3 has 2 side bars. Type 3R has no side bars but yours is the duplex, indicated by the sloping figures.
1384 - Clifton Hill. The non duplex RRRRR rated is the Roman numeral style, so MCCC over 84 with large figures. They later did a MCCC over 84 with smaller figures, then a straight 1384 duplex, which yours is. So not rated.
In your second group :-
98 - Malmsbury. Some better news here

This is the 1st duplex and has an R rating. So not the RRR Type A2, which has 2 side bars, but better than nothing. I'll explain the ratings at the bottom of the post for those interested.
1427 - Korumburra (the 7 has a prominent serif you can just see.) Duplex, not rated.
All I can tell you about the next one is that it's a NSW cancel. After 13 October, 1910, all stamps became interchangeable and could be used anywhere in the Commonwealth. Why that date is a long story involving "book-keeping" clauses in the constitution so each state wasn't disadvantaged when Federation took place in 1901. So you sometimes see other state cancellations for stamps issued or in use from 1910 onwards. Not that common, although not specifically rated. May attract collector interest.
Can't help with the last one, I don't do cds

For anyone not familiar with the ranking system to rate rarity, this is how it works:
NNR - Number not recorded. Means none have ever been sighted.
RRRRR - 1 to 3 examples thought to exist.
RRRR - 4 to 12 examples thought to exist.
RRR - 13 to 24 examples thought to exist.
RR - 25 to 50 examples thought to exist.
R - 51 to 100 examples thought to exist.
SS - 101 to 200 examples thought to exist.
S - 201 to 300 examples thought to exist.
So you can see that even your R rated numeral is pretty rare! Rarer than most stamps.
Balf