Yes, the change in the domain is allowed in the future. Only the simultaneous operation of the module on the number of domains exceeds the license limit is not allowed. If for example, a license for one domain, then the installation and work on two or more domains is considered a violation. Also, for the purpose of debugging, temporary operation is allowed on the test site if there is no access from the Internet, for example on a local server.
technical support is unconditionally carried out if there are errors in the software code of a paid module or plugin. In other cases, the answers are given in the form of leading tips and if questions relate to some features of the module / plug-in, and there are no responses to them in any FAQ installation installer or in prompts in the adminpanel of the module. Technical support does not apply to free refinement for the requirements of the buyer, work on layout, etc. Before contacting technical support, I urge to read the comments on the page of the module / plugin, as questions are quite often asked for which the response has already been given in the comments.
Yes, perhaps the estimated price for the hour of custom-made works - $ 45. The prepayment is a mandatory requirement. If these conditions are suitable - you need to write a literate TK, describe the module or what to modify, indicate which functions are needed, etc.
Unfortunately, the return in any case is impossible, this is a digital product, and not an ordinary product from a regular store. Buying any product on the site you agree with the appropriate paragraph from the license agreement, so carefully read the description of the module or plug-in before purchase
If your site is located on a virtual (shared) hosting, then the problem with access rights almost never occurs, since the hoster always configures the general server correctly. If you have a dedicated server and have problems with access rights during installation - most often this happens when the owners and groups of scripts and FTP do not coincide. At the time of testing, you can install these folders and rights files 777 recursively (this is a temporary solution) to ensure that the problem is caused. Then it is still recommended to figure out why such a situation arose. Completely helps the command chown , you can show this part of the text of the Hoster or the administrator serving your dedicated server - they will immediately understand what's the matter. In extreme cases, you can resort to manual installation, the process that enters the instructions for modules and plugins.