What is the alleged false reason behind Prince Harry's desperate demands for IPP (Intimate Partner Protection) for Meghan Markle and their family?

If another member of the royal family, for example the Princess Royal, was to represent the King on an international visit, she would be given IPP status for the duration of that visit. Most other IPPs only hold the status while they are performing certain duties, rather than around the clock for life.

IPP actually stands for International Protected Person. This is a status assigned to heads of state, heads of government, minister for foreign affairs, or the person representing a head of state/ government overseas, along with the family of the IPP in question. These people receive special protection when they are undergoing the duties of their role.

Prince Harry is not a head of state or a minister or ambassador, and as he no longer performs royal duties, he is never in the position of representing the King at any international event. He is not eligible for permanent or temporary IPP status and neither is his family. If he feels he needs security protection for his family, then he needs to pay for it himself.

How can a hacker damage me, realistically?

In relation to the British Royal Family, the King, Queen, the Prince and Princess of Wales and the Wales children are entitled to round the clock protection, because they are essentially on duty for life.