Support

a) https://www.akeebabackup.com/documentation/admin-tools/upgrade-to-pro.html - URL says that admin tools need to be installed twice, if upgrading from core to pro. I can see that the component has upgraded without any issue using install from directory. Do i still need to do this twice ?

I would suggest that you do. Many times Joomla! reports that the Core version was upgraded to Pro without a problem but it forgets to copy all files. That's why we ask you to install twice.

b) I have installed Marco Sql plugin earlier - can i unpublish it as if all security component as in marco is handles well by Admintools or does it work up differently

Please unpublish it. Admin Tools does a better job at implementing the same security features (and more!).

c) When i visit to this link on - Super Admin ID it shows 2 messages

JUser: :_load: Unable to load user with ID: 42 - in red

Congratulations! You are already using a secure Super Administrator ID. Click on the Back button to return to the Control Panel page. - in green

This is normal. It's an artifact caused by the way Joomla! works under the hood. You do not need to do anything else on that page.

Just download the ZIP file of the component and extract it.
Files under backend go into administrator/components/com_admintools
Files under frontend go into components/com_admintools
Files under media go into media/com_admintools

Look, the Joomla! bug is only triggered on very few cases. Based on the volume of support requests I've had it probably affects 5% to 10% of my users. That's still a lot of users. Installing the component twice in a row without uninstalling doesn't cause any problems so I'd rather leave that mandatory instruction in the documentation than having to provide support for the users affected by a bug I'm not responsible for and I can't fix. Since the bug doesn't cause any error message to appear users cannot tell the difference between a half-installed component and a buggy component. This leads them to write angry support requests telling me how much of an idiot I am to release obviously buggy software, asking their money back because I am a con man (this used to happen when Joomla! didn't copy certain files and the pro features wouldn't show up) and other similar very unpleasant things. These happened when the double installation was a suggestion rather than mandatory information. Do I want to go back to that situation? Hell no! I am many things, but a raging masochist is not one of them. So yes, I will kindly ignore your suggestion and keep this step as mandatory in the docs :)

Is it wise to autoblock these ip address

Yes, but don't block them using the blacklist. It's best to put a temporary, automatic block to them. How? Go to the Configure WAF page, look under the automatic IP ban. Please read our documentation, especially the Quick Setup and Configure WAF chapters. These are not mere documentation pages, they are a crash course to web site security. Take your time reading those chapters, you'll see what I mean :)