For question 1 – I don’t know about the PC version of Safari, but in the Mac version you can use the ‘Activity Viewer’ to see all the files on a page, one Youtube the movie file is easy to spot because it’ll be the biggest. Double clicking it will save it (confusingly with youtube all the saved files have the same name so you’ll need to rename it). You’ll then need something to covert it to a format suitable to burn on whatever DVD authoring software you use.

Q2 – yes you can switch sims – the phone number it attached to the sim not the phone. You can use different sims from the same network on a locked phone – so if your phone is locked to orange you can still use multiple orange sims. If its unlocked you can use any sim you like