@ Octavious:
A flying picket is a form of mobile secondary picketing where union members or supporters picket locations not directly related to the strike, generally at very short notice. So, it's kind of what you had in mind, yes.
The Labour Party has made no specific proposals to permit or legitimise flying picketing. There have been no publicly-reported meetings with trades unions on this specific issue. David Cameron is lying. He is a liar.
Now on your specific questions:
1. Britain has the strictest labour relations / trades union laws of any western european country. Workers in France, Germany, Spain and other EU nations have much wider rights in terms of their ability to organise and campaign. Jeremy Corbyn has suggested (in a recent BBC interview) that if elected to Government, he would repeal certain legal restrictions on trade union activity introduced under Margaret Thatcher in the 1980s. However, this is not what David Cameron claimed. David Cameron claimed that Labour had made a specific commitment to the trades unions, promising that he would legalise flying picketing. That was a lie.
2. Jeremy Corbyn is on record as saying that the Falklands should retain British nationality if that is what the majority of Islanders want. He has also said that a more constructive dialogue needs to be had with Argentina over the issue, in place of the sabre-rattling that has been the British approach since the war. Jeremy Corbyn has NOT said that he believes the Falklands should be returned to Argentina - and even less true is the claim that any such thing has been promised to Argentina. David Cameron is a liar.
3. Corbyn has stated that the number of refugees taken by each EU member state should be agreed at EU level, and certainly that the UK should take more than 20,000, since this is only a tiny fraction of the number of Syrian refugees entering Europe. This is a reasonable stance in my view. But it doesn't matter what I think. What matters is that David Cameron's claim that Corbyn promised ALL of the refugees currently in Calais that they could ALL come and live in the UK is 100% total and utter bullshit.
David Cameron is a liar. He is a lying liar who tells lies. He's despicable.