Q1. In order to access the no cost games you need to have an active PSNplus subscription. If you let it expire, you shed access. When you reactivate, you regain access. The games will normally be there, and you will be capable to play them as extended as you have a present PSNplus. Brief answer is “yes, they come back”
Q2. You do not essentially have to download the games in order to preserve them. You just click “add to library” and they turn into yours. When you are prepared to download them you just click “download” that could be that incredibly minute or months down the line. I normally (when I try to remember) add them to my library just to have. Some of the games are seriously superior, some are just “eh” but hey, they’re incorporated with your paid membership so why not.