IAS 11

You are correct that the IAS 11 is no longer in existence (let alone is it excluded from the syllabus!) The lectures to which you refer show some of the tricks often involved in the calculations of attributable profits and are therefore of great value to you In answer to your question "Is it necessary to listen to those lectures?", strictly, No, it is not necessary If you had asked instead "Is it advisable to listen to those lectures?" then the answer would have been Yes, it IS a good idea to watch and listen to those relevant lectures OK?

Yes, the new IFRS on Revenue Recognition IFRS 15, the one that replaced IAS 11 and IAS 18

You're welcome