Dear @Amxx ,
Thanks for reaching out. The 4.0 Smart Contract install issue has been fixed thanks to @abcoathup who advised me earlier on a separate ticket by performing:
npx uninstall @openzeppeling/contracts
npx install @openzeppeling/contracts
see 
Then when trying to verify the Previous Contract via hardhat, it was giving me compiling errors with 0.8.3 Solidity, the error literally stated that it did not fully support that version.
Hence I decided to downgrade the solidity versión to 0.8.1 within the code as well as within the hardhat.config.js and it compiled perfectly.
Therefore, I deployed a New Contract via Remix on Rinkeby See https://rinkeby.etherscan.io/address/0x94bc0a2916f06b56a330ea57154fe65a6a80ed42
and verified it via hardhat successfully. I have just tested the required functions (mint, pause, renounceRole, transfer, etc) inherited from:
"@openzeppelin/contracts/token/ERC20/presets/ERC20PresetMinterPauser.sol"
"@openzeppelin/contracts/token/ERC20/extensions/ERC20Capped.sol"
and they have successfully worked as expected.
I am ready to go to mainnet. Once deployed, I will update and give closure to this issue.