What are the practical implications of moving to 2.0.2 from 2.0.1?

I had the similar questions when moving from 1.3 to 2.0.1, about whether this was new software, whether old save files would be compatible, saving file in a different name to preserve old file versions, etc.
Questions:
1. Will this new move mean that 2.0.1 software is replaced or overwritten by 2.0.2?
2. Or will a completely new software be installed, to sit separately alongside 2.0.1?
3. Will I have to be careful to save files in a new name so a to preserve the 2.0.1 files for reference?
4. What happens if I say OK to the prompt - when I first access a file in 2.0.1 at present - about the new version? Will both the software and file itself be changed to the new software? Or do I x out of that prompt and go to the web page and download?

Could some one please go through the step by step process and explain the practical implications? Unless all is fully explained somewhere else - in which case let me know where?

Many thanks