First of all, we need to know what is Metatrader 4. Metatrader is a platform where you can do Foreign exchange trades. There are currently 2 types of MetaTrader. First one is the Metatrader 4 and the other one is Metatrader 5. Both versions are owned by the same company.
Metaquotes Software Corp. is a private company which is located in Cyprus. It was founded in 2000. Even though it has only above 50 employees; they have generated lots of profit due to their cooperation with retail brokers all around the world. Even though they seem to be located in Cyprus; it is originally a Russian company. Possibly they are using Cyprus for tax purposes and the original development is done in Russia.
Metatrader 4 is released in 2005. The programming code which was used was very similar to C. For example if you want to write indicators or expert advisors you need to know this programming language in order for MT4 to understand.
In 2010 Metatrader 5 was released. The programming language and the way developers wrote indicators and expert advisors had to change due to fit the new platform.
Even though Metatrader 4 is now very old platform it has been used by lots of brokers due to its reach by the retail traders. If you search online MetaTrader 4 indicators or expert advisors; you will find thousands of programs which you can run in the MT4. But if you do the same search for the MetaTrader 5 there would not be so many indicators for you to test its accuracy.
Because of MT4 popularity, we also started to learn MQ4 programming and started to give service to our clients in their trading journeys. We have faced very few MT5 requirements that is why we did not focus on that area. The most important logic that matters in your trading life should be your strategy, not the choosing of MT5 or MT4 platform.