Advice needed from a Joomla web developer regarding site admin security & back up

General information for the website: E-Commerce Web Site
Description of requirements/features: If I choose you for this work I will privately email you the questions and I will need written answers to be sent to me by email for various questions regarding how as the owner of a web site built in the latest versions of Joomla I can allocate an administrator status to a new web developer that does not give them the ability to change super user logins and passwords.

I also need advice on how I perform my own independent back ups of the web site to protect myself in general,

I need advice on how after allowing a web developer access and log in to my web hosting account I can protect myself against my web developer making unauthorised changes to my web hosting and web hosting account.

My web site was built by a developer who I no longer have contact with, so I would also like advice on what a new web developer requires to take over the web developing. E.g. Is access to the back end of the web site and to my web hosting account sufficient, or are there other things that a new web developer needs access to so that they can take over the web developing?

I would also need to be able to email you any follow up questions I have if I am unable to at first understand your answers or I am unable to implement your solutions.

For the person who I pay for the answers, I may possibly come back to you with more questions at a later stage, e.g. 1 or 2 months later, for which I would pay you additionally, or possibly make an arrangement with you for some ongoing technical support, because this would be a useful thing for me so that I can gain a second opinion on technical matters as a back up to the work that my new web developer will be doing for me.
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