Why is Testnet required and how to be a part of it??

You must have heard about testnet several times if you have been in crypto industry. Let's know about it in details.
Usaully, in app development or in any web development based on cryptocurrecny project, you need to write programming in langugae like solidity (EVM compatiable) and Rust (Solana) and many others. Let's say you writes alots of code and simply deploy it without testing it, then you might be somehow fallen into big problems.
Each things execution in programming related to blockchain will costs you a gas or transaction fee. To know it's actaully working or not , you have to deal with it in Testnet network first and then only deployed to mainnet. So ,testing networks will ensure :

1) Your programming validation ,logical testing.
2) Since ,the code replacements and several time hosting or upgrading will costs an extracharge , it's better to do all things in testnet and deploy in mainnet at the end of successful products.
4) Testnet provides a better way to do or we can say that feedback and bugs created on programming are usaully founded by testnet users.
5) It will helps to make optimal code with short and sweet programming strcutures. Lesser the code ,lesser will be fee.
3) Apart from it, testnet incentivizes programs are made to promote the projects and let  people know thier products will be soon available in mainnet soon so that they can use their products better. Testnet programs provides real experience of products earlier than it's been deploying in mainnet. To be able to participate in Testnet and get rewards, you must be following either some youtube channels or any other social media networks. 

This accouts on medium usaully posts about the most of Testnet and their updates https://medium.com/@OxThea.