you can skip through sponsor segments, but these are ads from youtube, not from the creator, and youtube will not let you conveniently skip through the ads. if implemented correctly, youtube could ensure that the ad is fully played, which would need downloading and automatic editing to counter.
yes, but if youtube only serves you the real video chunks after your client plays through the ad chunks (all in the same media stream to the client), theres gonna be some waiting involved, not like adblocking today where it is instant.