How to deal with Hangers/Out of Sequences/Activity changes?

this has NOTHING to do with chaning any dates.

out of secquence means just that. You started or completed  an activity sooner than the logic dictated ie.

activity A then Actvity B then Actvity C all tied together logically with finish to start relationships

[  A  ]------------------->[   B   ] -------------->[  C  ]    

for some reason you did NOT have to wait for B to finish before you could start or finish activity C

this is OUT OF SEQUENCE LOGIC this means that your original premis was incorrect or you just wanted to model it that way.

to correct this delete the relationship form B to C and make the relationship A to C. 

As far has hangers I am not sure of what you mean but if you mean activites that do not have relationships. There should bb no activities without succesors except the last one. If you need to tie the hangers into project completion or punch list or close out. 

• Out-Of-Sequence Progress - Ultimately, it’s our recommendation that instead of relying on the Progress Override and Actual Dates options to deal with activities that progress out of sequence, owners should specify the use of the Retained Logic option and require contractors to address activities that progress out of sequence on an activity-by-activity basis as it occurs and to make appropriate changes to the schedule logic to ensure that the project schedule matches the current construction

• Dangling Activities - In summary, the meaning of Mr. Hurst’s condemnation of “dangling activities” as per se improper CPM scheduling technique is clear and convincing when we consider the reality that the duration of activities cannot be estimated with certainty. 

Kandavel,

An out-of-sequence updated hanger activity, as I understand it, is an activity that you made progress on ahead-of-its-scheduled-dates. By updating it, you should pull the Actual Start date to earlier, to before the Data Date (MS Project: Status Date). Since it is a 'hanger' activity, it does not have any successors and no other tasks will be affected by this updating. Entering the appropriate Actual Start date is the only thing you need to do at first glance.

On second sober thought, hanger tasks indicate an incomplete network of logic, so you should also find its rightful successor(s) and link these successor(s) up to it. It is not unthinkable that you have hard constraint dates on those tasks (that should not be there), which may pull back those activities as well. If these activities are o nthe Critical Path, the project will shorten, which may allow you to deliver your entire project early.

Hanger tasks should not exist; there can only be ONE hanger task in a schedule: the Project Finish milestone. 

In summary, there is a lot of things you should do:

1) Enter correct actual start

2) Find its successors and create these links

3) Check to verify if there are any inappropriate constraint dates on any of the successors, and, if so, remove them

4) Check your Critical Path to see what happened to it, if anything. If it shortened, then deliver early if you can.

Hope this helps! Thank you for this interesting question; there was more to it than I thought at first glance.