New Study feature - a few feature requests

First of all, wow!! Study is such a well done feature! Lichess was already amazing and now it's getting even better. Thanks to all of those who worked so hard on it so that we can all use it for free!

I had a few feature requests that I (and maybe others?) would find useful.

1) Is there a way to temporarily turn on puzzle mode on your own studies (and later turn it off)? It would be nice to be able to create a study for an opening line that I want to memorize, and then practice it to see if I can remember the moves. Right now the moves are always shown for my own studies even when I switch to puzzle mode.

2) Sometimes in the comments to a move, I would like to add a link to another webpage, or even embed a YouTube video that explains the position. Right now the URL does not automatically become a link...but could it? And could we embed a YouTube video (or maybe a video from the lichess video library) directly within Study? These would be great ways to quickly navigate to related content that is outside of the Study.

3) Is there anyway to undo the previous edits to a study? It seems that sometimes you get a confirmation message when deleting a variation (if it contains a comment?), but other times there is no confirmation and no way to recover the deleted moves. If undo is not possible, could it be possible to view my own study in read-only mode so that I don't accidentally delete anything?

Thanks again for making lichess amazing and free!!

Strong support for 2)!

more precise: for autoconverting links, preferable with names, like [name of the link](http://url/of/the/link)
Im fine if these are lichess only links (to prevent spam).
also, linking to specific chapters would be awesome.
I dont care for embedded videos.

Nice job, Thibault.

or [name of the link http://url/of/the/link] is more common i think ...

Also, would be nice to be as in the challenges: 'Let other players invite your to their studies' – Never; If rating is ± 500; Only Friends; Always.
And... when a game is finished, could you guys import the already done computer analysis (blunders, mistakes, avg centipawn loss etc) to a study?

one more word to #3, the background is, that one could create studies which contain common motivs, well explained, and then he could create eg. shortened opening studies and comment the end of a variation with like: 'white is better because of [m4 link/to/a/motif]. Black has to defend like in [m7 link/to/another/motif]'.