docs/user-guide/time-and-costs/time-and-costs-faq/README.md
It is not possible to prevent time logging on phases or restrict it to certain work package types. You could deactivate the fields "Work (earlier called Estimated time)" and "Spent time" for type Phase (using the work package form configuration) but it would still be possible to log time for Phases.
Since 12.2 release it is possible to log time for a user other than yourself. This right has to be granted by an admin to users with certain roles. You can find out more here.
Yes, it is possible to see all hours assigned to each user in total. In your cost report you would just need to select all projects that you would want to look at. Click on the + next to the project filter, select all projects or the ones that you would like to select (use Ctrl or Shift key), choose all other filters and then click Apply to generate the cost report.
Unfortunately this is not possible at the moment. There's already a feature request for this on our wish list here.
Yes, you can use the "My spent time" widget on My page and use the filters there.
No, it is not (yet) possible to log time in days or any other units besides hours. However, you can use decimal places, like 0.25 hours.
Yes. The Resource management module enables project managers to plan capacity, allocate work and staff projects based on team members' availability and skills. For details, see the Resource management user guide.