Explanation:
Box 1: Yes
Microsoft guarantee at least 99.9% availability of the Azure Active Directory Premium edition services. The services are considered available in the following scenarios:
* Users are able to login to the service, login to the Access Panel, access applications on the
Access Panel and reset passwords.
* IT administrators are able to create, read, write and delete entries in the directory or provision or
de-provision users to applications in the directory.
Box 2: No
No SLA is provided for the Free tier of Azure Active Directory.
Box 3: Yes
You can claim credit if the availability falls below the SLA. The amount of credit depends on the availability. For example: You can claim 25% credit if the availability is less than 99.9%, 50% credit for less than 99% and 100% for less than 95% availability.

Explanation:
https://www.microsoft.com/en-us/trust-center

Explanation:
Box 1: Yes
The tool you would use to sync the accounts is Azure AD Connect. The Azure Active Directory Connect synchronization services (Azure AD Connect sync) is a main component of Azure AD Connect. It takes care of all the operations that are related to synchronize identity data between your on-premises environment and Azure AD.
Box 2: Yes
As described above, third-party cloud services and on-premises Active Directory can be used to access Azure resources. This is known as `federation'.
Federation is a collection of domains that have established trust. The level of trust may vary, but typically includes authentication and almost always includes authorization. A typical federation might include a number of organizations that have established trust for shared access to a set of resources.
Box 3: Yes
Azure Active Directory (Azure AD) is a centralized identity provider in the cloud. This is the primary built-in authentication and authorization service to provide secure access to Azure resources.
References:
https://docs.microsoft.com/en-us/azure/active-directory/hybrid/how-to-connect-sync-whatis
https://docs.microsoft.com/en-us/azure/active-directory/hybrid/whatis-fed
https://docs.microsoft.com/en-us/azure/active-directory/develop/authentication-scenarios

Explanation:
https://docs.microsoft.com/en-us/azure/azure-resource-manager/management/lock-resources