Can I charge the customer for software? This includes selling the software as well as charging for technical support?
Yes, you can sell software that is licensed under the GPL v3. Section 4 addresses distributing verbatim copies. You must keep the copyright notices and licenses and give all recipients a copy of the license. When selling the software, you can choose to charge a fee for distribution, provide warrantees, or offer support packages.
If the software is known by name 'ABC', can I change the name of software to 'xyz'.This may include changing the logo, name on the UI?
Your changes would be a derivative work and covered by Section 5 of the GPL v3. You must add notices that you have modified the software and you must license your derivative work under the GPL v3.
Do I need to provide the copy of source code voluntarily? I am fine to provide the source code if some body asks for it.
Section 6 of the license addresses this. If you do not distribute the source code with the executable object code, you must provide the license and a written notice about how to obtain the source code. There are some caveats as to what is acceptable if you are providing the software as part of a commercial offering.
Is it necessary to publish the modified source code if I host it in the cloud?
No. Usage over a network does not count as distribution, and you only need to provide the source code to people who receive your executable object code. This "gap" led to the creation of the GNU Affero General Public License.