MetaQuotes is currently working on the latest trading platform MT5 platform, but MT4.
MT4 is being version upped to fix bugs and for other updates periodically, but the company now wants the traders to try out the MT5 platform.
Thus, all the download links in MetaQuotes Official Websites are replaced for MT5 trading platform, and you cannot download the MT4 platform anymore. (there are still pages and links which mention about MT4 platform, but download links are not for MT4.)
To get the MT4 trading platform, you will need to find a FX broker with MT4.(See the list of MT4 brokers here.)
From each MT4 brokers, you can always get the latest version of MT4.
You can also use the MT4 of a specific broker, for MT4 accounts of other FX brokers.