The answer to your questions for all the three cases are left for the operator's discretion.
What I understand is that if the operator assigns Youtube, Skype and Whatsapp , all to one PDN and allocates a Default EPS Bearer ( to assign IP Address ) and a dedicated EPS Bearer ( with Non-GBR QoS for Internet access ), that thats all you are going to have.
If the operator assigns a separate PDN for streaming and multimedia service then you may have to connect to a separate PDN to access Youtube.
How the Bearers will be allocated is totally decided by operator. The specifications only provide provisions to add, modify and delete them based on operator defined policies.