I need help in IT security & policies area please, appreciate supporting me on the below:

$1-$ What is the concept of a zero$-$day vulnerability, and why is it particularly dangerous? Give a real example of zero$-$day attack in recent years and its impact.

$2-$I need some real$-$world examples of organizations that have successfully implemented CMM$,$ and how did achieving higher maturity levels impact their project outcomes and business success? Appreciate if the source as a proof is provided if possible

$3-$ How do firewalls and intrusion detection$/$prevention systems $($IDS$/$IPS$)$ work together to defend against network$-$based attacks? Provide one example of an attack that can be mitigated by these security tools.

$4-$ What are the key security risks associated with storing sensitive data in the cloud compared to on$-$premises data centers, and how can companies effectively leverage encryption and access control to mitigate these risks? Additionally, what delineations of responsibility exist between the company and the cloud provider in ensuring the security of cloud$-$stored data?