Transferring activities associate with accounts to lead

Question

1) On changing the "whoId" of the activities for the conversion of activities associated with the account to lead should we also change the "whoId" field of open activity and activity history too?

2) If I empty the "whatId" of the activities associated to account and delete the account will the activities get deleted?IF yes is there another way from preventing this activities deletion?

3) Finally while importing the activities from workbench or dataloader should we update it by selecting the Task and Event object seperately? Or is there another way to perform this?

Answer 1

N.B. All these questions could have been answered by a little experimentation

1) On changing the "whoId" of the activities for the conversion of activities associated with the account to lead should we also change the "whoId" field of open activity and activity history too?

YES; the WhoId on the Account is probably a Contact or User and now you want it to be a Lead

2) If I empty the "whatId" of the activities associated to account and delete the account will the activities get deleted?IF yes is there another way from preventing this activities deletion?

Deleting the Account will delete any children Activities. But an Activity without a WhatId pointing at that Account will no longer be a child of that Account so the Activity shouldn't be deleted

3) Finally while importing the activities from workbench or dataloader should we update it by selecting the Task and Event object seperately? Or is there another way to perform this?

There is no DML'able SObject for Activity. you have to do Task and Event separately