In answer to your questions:
1. No, it is not compliant, because sheathed (a.k.a sleeved or insulated) earth pins are not permitted. There may be other discrepancies that we cannot see so easily, as the manufacturer has not apparently taken notice of the standards nor submitted the design for testing.
2. The sleeving / sheathing on a contact pin is the plastic collar around it nearest the body of the plug. This is required on the line and neutral pins of current production plugs (old ones did not have them) to prevent fingers contacting the pins while inserting and withdrawing the plug, and causing an electric shock. The earth pin is safe to touch therefore does not need sheathing.
3. When used with an earthed appliance, a sheathed earth pin can prevent it making contact in the socket, leaving the appliance without an earth connection. The design of a socket earth contact is usually different to that of the line and neutral in order to ensure it makes contact first when a plug is inserted. Therefore it tends to rely on the part of the earth pin nearest the plug body and will not work with a sheathed pin.
In this case the cable is 2-core for use with a double-insulated appliance and the earth pin will not be connected and need not make contact. The normal and correct method where an earth connection to the plug is not needed, is to use an ISOD (insulated shutter opening device, i.e. solid plastic pin) in place of a metal pin. The reason a sheathed earth pin is still unsatisfactory is that the plastic collar can catch on and damage the socket contact, reducing its efficiency when a compliant plug is later inserted.
Note: BS1363 is a standard, not an approval. It does not indicate a product is safe, it merely tells the manufacturer how to make it so. Whether they follow it is another matter - I could stamp BS1363 on a metal skewer but that does not make it safe to insert into a mains socket. What you are looking for are approvals, from recognised testing and certification bodies, showing that the device has been tested and found to comply. There are no approvals on your plug; there can't be as it's non-compliant. However manufacturers are known to print fake approvals on goods too, so even the presence of a recognisable approval is no cast-iron guarantee without the supporting documentation.
In summary - the plug is non-compliant and carries no approvals. It could possibly damage a user's socket. Since non-compliant items are often non-compliant in multiple ways, there may be other unseen problems.
