All tools are purchased through the MQL5 Market (link). I can't help with purchases, installation, refunds and so on, as this is all handled by MetaQuotes. There are videos at the MQL5 website on how to do these things.

If you've purchased a tool from the MQL5 Market (link) and changed your mind before you've activated it, then you can get a refund by going to your profile and checking the list of your purchased tools. There will be a link there to cancel the order of any tools that have not been activated yet. Once you've activated it they do not provide refunds.

You get 10 activations per tool. An "activation" means that you can install it on a computer. This is not tied to a broker, an instance of MT4 or a trading account. Once you've installed it for one MT4 on your computer you can install it on any number of other MT4 instances, brokers or trading accounts, on the same computer, without using additional activations. Once you've used all 10 activations it would be necessary to re-purchase to install on any further computers.

XX will work on any chart that you can open in MT4/MT5. No matter what instrument you’re using it with, you should test it to understand if it’s giving you feedback that you can successfully use to trade. You are the trader, you are ultimately responsible for every trade you take, even when informed by indicators. Once you are comfortable with what the indicator is telling you, you should trade demo to verify in forward testing conditions before risking your capital. (In case it's not clear, "XX" means any of the various indicators or EAs that I sell. Or, you know, in general.)

No, you cannot. Third-party indicators, EAs and scripts are not compatible with the mobile versions of MT4. You can set up your MT4/MT5 to send you push notifications that you receive on your phone, but there’s no direct support on your phone for the indicator/EA itself.

There are two usual reasons for this. The first common problem is that the symbol name in Market Watch uses a prefix (xxxAUDCAD) or a suffix (AUDCADyyy), and because the names don’t match, there’s no data. There are input parameters in most tools to set a prefix or suffix, you need to configure this in your settings. This could also be because your terminal doesn’t have data loaded for all of the symbols being used yet. You can force the terminal to load data by opening a chart, turning off auto-scroll, and hitting the Page-Up key repeatedly to go back in time, forcing the terminal to load that data. Load each chart that you’re using, at least 10 days worth of data (for calculating ADR). Also, each symbol needs to be available in Market Watch.