I have fixed the error. The Solutions Lies in what @Toufiq has narated but we have to apply mind onto it. Step By Step, please swich off external installation and then we have to proceed with the error tutorial.
What I am not getting is that will the Site work on 7.4 ? The answer is yes. It will work only when yoiu fix the border radious issue first. Then once we complete that, we should be able to upgrade the database back again.
Once you do htat, go to SP Page Builder pro and click maintenance. It will ask you to upgrade the data base of your Joomla Installation. Then this will be able to handle the update to the database.
of course we are tricking the system to believe all is well, but it will work.
best wishes.
Closing this ticket.