when using email 2.0 template in the email you delete an asset or a content asset, can you undo it (ctr/cmd+z)?
For example, if I deleted one of our brand logos assets in the email when using custom 2.0 template, can I undo it, or I should create new email if I want to use that asset?
Ctr/cmd+z does work when editing email templates in 2.0 -- but only as long as the current window is active -- if you close the window (ultimately save+close because it saves automatically) then everything is committed and there is no undo. I'm not sure if that fully answers your question though?
On top of JD's answer, always remember that when you edit an email that had been approved in the past, Marketo will always create a draft. This means that, until you have approved the draft, you can always revert to the previous (production) version of the email: for this, simply delete the draft.