One big difference between Sky catchup and other systems is that, for Sky+HD viewers at least (I think it’s different for Sky Q) you don’t stream the content, you download it and watch the recording as if it were a PVR recording.
That's been the case ever since Sky on-Demand launched which gives it the advantage as you say over streaming because you just download it once to the box and watch it as many times as you want regardless of whether the internet's working on it. Works in the same way for Sky Q I believe.
This approach is what makes it suitable for any speed of internet connection because its only used to get the programme. So somebody unfortunate enough to be stuck on a 1Mb connection can still use Sky on Demand, it'll just take longer to download enough to get to the point where one can play it all the way through without stopping.
That has one big implication- you can fast forward through any adverts. In fact Sky includes adverts at the start of some of its catch up/box sets contents sometimes (though usually no more than a promo, ident, and sponsor bumper).
Last time I checked this I believe they were looking at using the Adsmart technology rather than just embedding a bunch of adverts that would become outdated after a few weeks. However Adsmart only works if you play the ads at normal speed not fast-forward.
With regards to the "stop you skipping adverts" - it must be possible, after all you can't use the Sky+ Pause or rewind when the BBC One HD "turn to channel 101" slide appears BUT you can reel back through it and pause it after the event, just not at the time. So on this basis I presume since its possible to temporarily override Sky+ for the purposes of that slide it should be possible to do the same on the commercial channels on catch-up. In theory.