[tristor]

Even if it's legal I wouldn't put up with that, and something that extreme would need to be detailed thoroughly in the lease agreement. If it's not, you didn't agree to it, and I'd be telling them to leave or you'll be calling the police to have them arrested for trespassing. Then I'd be moving ASAP and suing them for breach of contract and a return of previous rents.

Generally, at least in the US (every state differs slightly) a landlord or their agent can enter your apartment only in an emergency circumstance or with your explicit permission after requesting. The only time they'd take photos is after you've moved out to photograph damages for evidence if they with hold any part of your deposit. Your landlord should not be snooping around your house every 90 days, that's ridiculous. In the US, it's common to change the locks on the door after renting and then turning in the new keys when you leave.

[rsgrn]

I would like to not put up with it, hence asking questions to see if they actually understand what they are doing...

It is also during period inspection, so they have asked to attend and it has been agreed.