Explanation:

Box 1: Yes
The following list provides advantages to using aggregations:
Query performance over big data - as users interact with visuals on Power BI reports, DAX queries are submitted to the dataset. Boost query speeds by caching data at the aggregated level, using a fraction of the resources required at the detail level. Unlock big data in a way that would otherwise be impossible.
Box 2: No
You can connect to model-driven apps in Dynamics 365 with Power BI Desktop to create custom reports and dashboards for use with the Power BI service.
You can use similar steps to connect to model-driven apps in Dynamics 365 using Office Excel Power Query by selecting From Other Sources on the Power Query tab in Excel.
Box 3: Yes
Using the PowerApps custom visual, you will be able to pass context aware data to a PowerApps app which updates in real time as you make changes to your report.
Reference:
https://docs.microsoft.com/en-us/power-bi/desktop-aggregations
https://docs.microsoft.com/en-us/power-platform/admin/use-power-bi
https://powerapps.microsoft.com/sv-se/blog/powerbi-powerapps-visual/