Getting onto a motorway from a slip road

I have passed my driving three months ago and I'm now planning to go on a short trip using the motorway. I know slip roads are there to gain appropriate speed before joining a motorway's left hand lane....

Does stopping distance increase with heavy electric cars?

Are electric cars heavier than their petrol and diesel equivalents? If so does the extra weight mean they take longer to stop? If so is thus a road safety hazard?

I've been told you should never brake if you have a tyre blow on the motorway - is this right?

I read that if your tyre blows out when driving on a motorway you should never brake but go to a lower gear and try to steer the car to the hard shoulder. Is this sound advice?