[SalesForce] List of all fields with history tracking enabled for Case object

Create an object called AccountHistoryTracking and fields like APIName__c,OldValue__c,NewValue__c then create a fieldset on Account called'HistoryTracking' with the fields you want to track on Account and then write below code to track history on account.This way you don't need to worry about history tracking limit per object.

trigger AccountHistoryTracker on Account (after update) {

    final List<Schema.FieldSetMember> trackedFields = 
        SObjectType.Account.FieldSets.HistoryTracking.getFields();

    if (trackedFields.isEmpty()) return;

    final List<AccountHistoryTracking__c> fieldChanges = 
        new List<AccountHistoryTracking__c>();

    if(!trigger.isUpdate)
        return;

    for (Account newAccount : trigger.new) {

        final Account oldAccount = trigger.oldmap.get(newAccount.Id);

        for (Schema.FieldSetMember fsm : trackedFields) {

            String fieldName  = fsm.getFieldPath();
            String fieldLabel = fsm.getLabel();

            if (newAccount.get(fieldName) == oldAccount.get(fieldName))
                continue;

            String oldValue = String.valueOf(oldAccount.get(fieldName));
            String newValue = String.valueOf(newAccount.get(fieldName));

            if (oldValue != null && oldValue.length()>255) 
                oldValue = oldValue.substring(0,255);

            if (newValue != null && newValue.length()>255) 
                newValue = newValue.substring(0,255); 

            final AccountHistoryTracking__c accountHistory = 
                new AccountHistoryTracking__c();

            accountHistory.name         = fieldLabel;
            accountHistory.apiName__c   = fieldName;
            accountHistory.User__c      = newAccount.Id;
            accountHistory.ChangedBy__c = UserInfo.getUserId();
            accountHistory.OldValue__c  = oldValue;
            accountHistory.NewValue__c  = newValue;

            fieldChanges.add(accountHistory);
        }
    }

    if (!fieldChanges.isEmpty()) {
        insert fieldChanges;
    }
}

History Tracking for Task object is still an Idea. You need to implement custom apex solution for it.

Or you can vote for the idea here https://success.salesforce.com/ideaview?id=08730000000BpqcAAC

It is there for 6 years.