Question on Critical Damage

On body armour, there is a soul modifier suffix - “Hits against you have have 10-99% reduced critical damage bonus”

Gemling has a node called Gem Studded that grants “Hits against you have no critical damage bonus”

For non-gemlings, You could hit >100% reduced critical damage bonus with the soul suffix combined with skill tree or soul core.

I think this is a very strong defensive layer for non-gemlings but have not seen people discussing/ using this.

Q1) Is “hits have 100% reduced CDB” the same as “hits have no CDB”?

Q2) What happens when there is 120% reduced CDB? Will it have no additional effect?

Q3) What happens when a monster has 200% increase CDB and you have 100% reduce CDB?

Q4) What happens when a monster has 100% increase CDB (default value) and you have 120% reduce CDB?

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Example scenario: Monster normal attacks for 100 damage. When critical, it is 200 (double damage). With 200% increased CDB, it is 300.

Having Gem studded, the damage would be 100?

Having 100% reduced CDB, the damage would be 100?

Having 120% reduced CDB, the damage would be 83.33?

Thank you.