IF the client asks me for a estimated time for completion for the whole project can this be given using Scrum?
Using for instance the (dreaded) waterfall methodology I will have a technical spec to use to give a half decent estimation.
Yes, you can (and do) estimate Scrum projects. [Note "Scrum" is an English word, not an acronym or abbereviation. It should not be in all-capitals.]
You estimate a Scrum project this way.
Write down the backlog.
Break the backlog into sprints.
Prioritize the sprints from most valuable to least valuable.
Provide this prioritized list of sprints to the customer.
They are free to stop work at any time, since each sprint is useful and the first sprint is the most useful and important part of the system.
That's the estimate. It's theirs to manage.