Blockchain technology, improvement suggestions, security challenges on smart grid and its application in healthcare for sustainable development

Blockchain technology has gained considerable attention for different types of stakeholders due to its stable implementation in the field of digital currency like Bitcoin. Some users use Bitcoin for payment exchanges against any business while others use the Bitcoin network for earning Bitcoins itself, and there is also another type of user who called hackers those flood different types of attacks to illegally earn some Bitcoins or collapsing overall network. There are also numerous uses of blockchain technology, e.g. health, automation industry, energy sector, security and authentication in smart grids. In this study, we have elaborated on different critical aspects of Blockchain technology like its style of working mechanism, possible improvement suggestions by using Proof-of-Stake, and other custom variations, attempting seven types of challenges by different novel techniques. Moreover, we have also explained the current state-of-the-artwork in blockchain's non-financial applications like Healthcare in which contribution of four-layered custom blockchain models related to precision medicine and the clinical trial was notable. Moreover, a mobile app model called HDG for the automation of medical records without compromising privacy was also a prominent contribution.