Can s90 seats be fitted to S60

[IMAY2023]

Which PINs are you asking about? 
On the controller itself or on the Seat harness to Car's body connector? 

If you are asking about the Seat to Car harness connector.
Driver side connector:  94/505 
Passenger Side connector: 94/506
94/505:16 and 94/506:15>  15/50 CENTRAL JUNCTION BOX connector A30 (fuse number 40, 5amp)
94/506:11 From 7/255 SEAT BELT REMINDER MAT (power) > 4/176 SUPPLEMENTARY RESTRAINT SYSTEM SRS on F6.  (passenger side only) 
94/506:31 From 4/240 OCCUPANT WEIGHT SENSOR OWS  (LIN) > 4/176 SUPPLEMENTARY RESTRAINT SYSTEM SRS on F92.   (passenger side only) 

It looks like your new seats have occupant sensor and seat belt reminder but your old seats do not have. You can ignore them and just do not enable those from Orbit.  
But it just does not make sense. you are missing the main PINs, (CAN BUS, Power, Ground and some other stuff) even from the new seat's connector. 
Have a look the diagram. https://forums.spaycetech.com/attachment.php?aid=334 and search for  94/505:XX  94/506:XX  where XX is the PIN number on the connector.

[Helpful]

While I'm waiting for that mountain of spare parts that still need to be installed on my new seats (to make everything simple), I found another question. And these are the rear headrests. Now in my car the rear headrests fold with a physical button on the back of the seat. But in the new seat the headrests are already electric (the ones that fold with a button in the system menu). Perhaps this has already been discussed on the forum, if so, please give a link. Or how to solve this issue to integrate a new seat with an electric headrest?

[IMAY2023]

On the rear seats, you should have connector. PIN 5 is the ground and the PIN2 is the folding headrests. 
PIN2 on the LEFT goes to the CEM PIN FL75
PIN2 on the RIGHT goes to the CEM PIN FL76 
Then, you will need to set the 187  HEADRESTS 2nd ROW, FOLDING to 02. Which will give you the virtual button on the car functions page.

[Helpful]

On the rear seats, you should have connector. PIN 5 is the ground and the PIN2 is the folding headrests. 
PIN2 on the LEFT goes to the CEM PIN FL75
PIN2 on the RIGHT goes to the CEM PIN FL76 
Then, you will need to set the 187  HEADRESTS 2nd ROW, FOLDING to 02. Which will give you the virtual button on the car functions page.

@IMAY2023 If it's not too much trouble and you have a minute, could you describe to me what I need to add for the rear seats and how to lay the wire.

I have seats without heating and with mechanical headrests. New seats with heating and electronic folding headrests.

I have read your 4th message many times and I still can't figure it out.

For heating. Is it necessary to lay some kind of wire from the central tunnel (where the heating buttons are) along the cushion and back of the rear seat?

Along the headrests. Did I understand correctly that CEM PIN FL75 and CEM PIN FL76, it is necessary to lay the wire from PIN2 on the connectors of the backrest to the CEM itself, which is on the front panel? Is it possible to somehow replace this and install a beautiful mechanical button on the back of the seat (in my opinion, this is even more convenient than the electronic button on the "TV")?

[IMAY2023]

@IMAY2023 If it's not too much trouble and you have a minute, could you describe to me what I need to add for the rear seats and how to lay the wire.

I have seats without heating and with mechanical headrests. New seats with heating and electronic folding headrests.

I have read your 4th message many times and I still can't figure it out.

For heating. Is it necessary to lay some kind of wire from the central tunnel (where the heating buttons are) along the cushion and back of the rear seat?

First things first. 
The rear heated seats are controlled by 2 LIN slave modules (left and right) and they are on the same LIN as the front seat heater modules (left and right).  
Each module receives Power from the rear fuse box and negative from the body goes the backrest heater pad (If I recall correctly).  Check the wiring diagram. https://forums.spaycetech.com/attachment.php?aid=335  Don't worry about the S/V90 series, it's the same for all models and year when it comes to seat climate. 

You did not mentioned if you already have 4 zone climate or just 2 zone. If you have just 2 zone. You need to buy rear seat heat buttons and connect it to the existing free connector but it does not have power and LIN on the other side. (where senter console connects to the car's main wiring. (passenger side behind the cover).  The button shares the LIN with the drive mode switch and the power, I took it from the lighter connector.  If you have 4 zone, you just need to change the digital panel with the rear heated seat version. 

Along the headrests. Did I understand correctly that CEM PIN FL75 and CEM PIN FL76, it is necessary to lay the wire from PIN2 on the connectors of the backrest to the CEM itself, which is on the front panel? Is it possible to somehow replace this and install a beautiful mechanical button on the back of the seat (in my opinion, this is even more convenient than the electronic button on the "TV")?

You can try, all you need negative and positive connected to the backrest connector PIN2 is power and PIN5 is negative.