Backtest is very dependent on your tick data quality.

Metatrader 4: If you are using MT4 then you need good quality tick data. By default Metatrader 4 does not provide good tick data quality and you MUST use data from some external source. If you want to get 99% tick data quality for free you can tutorial in this article: Back-testing with 99 % modelling quality for FREE. Please note that MT4 data even if it is downloaded from external source does not include real spreads. It is always fake no matter where you download the data from.

Metatrader 5: If you are using MT5 then you don’t need tick data from some external source but you need a good broker. For MT5 the data is provided by your broker including real spreads. When you run the backtest select modelling “Every ticks based on real ticks” and after the backtest finishes you should see the data history quality on “Results” tab. Good brokers can provide up to 100 % history quality for past years.

NOTE: With increasing backtesting period to the past the history quality usually decreases, so keep in mind that it is only backtest and real performance may vary.

If you want to know how to properly run a back-test read article: How to use Strategy tester in Metatrader

When update it released the MQL server notifies users immediately, but apparently there is some delay between the update is published and download is available. So please wait some time and you will be able to download the updated version trough your Metatrader terminal from “Market” tab. Also make sure that you are logged in in your Metatrader terminal with your MQL community ID.