is it possible to retain local variable or rule input values after which gets refreshed during Submit action and use them before submit action gets completed?

I do not understand what you are trying to do here. We need more details.

we have given a list of Task along with deactivate icon (minus-square rich text icon), for this icon submit link has been used so that if user want to deactivate any task, then user can click on that icon and soft delete that task from list
Now current requirement is like when we click on deactivate icon it should not get deactivate if that task is used and dependent task for any other task in the list and a validation error msg should be shown under that task to user notifying this dependency
So due to this Submit link, all local variables or rule input gets refreshed and lose their updated value which holds the results for checking dependency, current task name for which deactivate icon has been clicked, because of this we are not able to show the validation msg for desired task 

Issues i am facing are:

- with Submit Link / Button: 

it executes the Deactivation action for non-Precedent Task 

but fails to show validation msg on UI (in Design interface validation msg is showing up)

-with Dynamic Link:

successfully shows the validation msg on UI if task is used as precedent task, but fails to deactivate task which is not used as precedent task

The requirement can be achieved without the submit link. Instead we can use a!dynamicLink() and in saveInto(), call the a!writeToDataStoreEntity(), if the conditions satisfy to soft delete the task. If the conditions does not satisfy, show the validations. In case you want to update some other details like audit during soft delete, you can still achieve this by using a!startProcess() in the dynamicLink saveinto.

The requirement can be achieved without the submit link. Instead we can use a!dynamicLink() and in saveInto(), call the a!writeToDataStoreEntity(), if the conditions satisfy to soft delete the task. If the conditions does not satisfy, show the validations. In case you want to update some other details like audit during soft delete, you can still achieve this by using a!startProcess() in the dynamicLink saveinto.

tried  implementaing this, saveInto is not accepting a!startProcess()
and for a!writeToDataStoreEntity() we need to give DataStore Entity, for defining entity we need CDT and we are not using CDT for defining tables

Here is an example for the saveInto:

Also you can you use a!writeRecords() in lieu of a!writeToDataStoreEntity().

A component saveInto will accept a!startProcess(), also if you are using records, you can use a!writeRecords().