Redmine

I tried redmine features, would like to know if following is supported/or what could be the best way to implement them-

It is quite easy to create an execution plan for a project, but executing it faces unplanned challenges.

Lets say I have created a 2 months plan with multiple versions and tasks on redmine .
1. Now what if version1 client feedback requires some new features? shall all remaining milestones and task dates be changed?- Not a good idea.
2. what if if a 2 day task actually takes 5 days because of some reason(lack of planning, resource unavailability, or some other priority work availability)- How to manage it.
3. what if If a 2 day task is running due (it shows as red on my Gantt chart), but when that is finished after 7 days it becomes green in my Gantt chart- No way to identify late finished task for performance analysis.
4. Gantt report doesnt tell how many times and why time lines for tasks/versions needed a change because of poor planning/unplanned priority work/poor estimate at project start. So that those problems could be identified, analyzed and not repeated again.
5. What are the good plugins for finished projects analysis about estimated and actual time consumption.-
(there are baselines in microsoft project to compare estimated and actual plan)