All hidden cats
Living room
#1: Click the the top left drawer of the cupboard left of the door
#2: Click the 3rd square drawer of the cupboard to the right of the door
#3: Click the curtains to open them
#4: Click the middle drawer to the left of the clock
#5 &6: Press the middle drawer of the most right cupboard.
Bathroom
#7: Click the top lid of the toilet
#8: Click the radio
#9 Click the mirror above the sink

All Hidden cats
Living room
#1: Click the mouse hole left of the door
#2: Click the plate thats on the lower part of the door
#3: Click the dome on the left branch
#4: Click the shutters
#5 &6: Click the bottom drawer below the window
#7:Click on the vent ඞ above the bathroom door
Bathroom
#8: Click the right drawer in the top left
#9: Click on the bin left of the toilet
#10: Click on the top left drawer below the sink

All hidden cats
Living room
#1: Click on the bag on top of the closet on the left of the door
#2: Click the right drawer of the bookcase
#3: Click the drawing that's on the round table
#4: Click on the bin to the right of the couch
#5: Click the cristal ball on the table
#6: Click the screen to the right of the bookcase
Bathroom
#7&8: Click the bottom left and top right drawers under the mirror
#9: Click the middle mirror
#10: Click the hole in the ceiling

Living room
#1: Click the painting left of the door
#2: Click the lightswitch left of the door and look for the light in the middle of the ceiling
#3: Click the botton drawer of the desk under the monitors
#4 &5: Click the power button on the PC next to the 3 monitors
#6: Click the wooden plank on the bathroom door
#7 &8: Click the door of the closet to the right of the bathroom door
Bathroom
#9: Click the glass cabinet
#10: Click the towel above the toilet

Note: There is a cat hidden on top of the closet left of the door and might be hidden behind the cat counter.
All hidden cats
Living room
#1: Click the top left cabinet just right of the door
#2: Click the left glass door of the cabinet, to the right of the bar
#3 &4: Click the 2 middle pillows
#5: Click the right circle (smokedetector?) on the ceiling above the bathroom door
#6: Click the cabinet door above the fishtank
Bathroom
#7: Click the window on the left
#8: Click the middle-bottom drawer under the sink
#9: Click the litter box
#10: Click the square on the closet, just above the litter box

To get to the roof you must go to the 5th floor and instead of clicking on the door, click on the stairs to the right.
No hidden cats, if you clicked on Fofiño in each room, they'll be in the middle of the roof

Hidden cats
Living room
#1: Click the opening on the cathouse to the left of the door
#2: Click on the TV to the right of the door
#3: Click the container below the TV
#4: Click the drawer on the right of the desk
#5: Click the middle pot on top of the rack
#6&7: Click the 2 pots on the top right of the rack. the highest and the 3rd most left
#8: Click the small cup on the right desk
#9: Click the drawer on the most right desk

Bathroom
#10: press the pillow on the bed
#11: press the boot on the ground
#12: press the cup on the left table

On floor #0 aka the title screen, there is a cat hiding next to the building behind a bush.
Click it to get the achievement!

Go to the credits trough the menu, press the cat hiding behind Giovani's name.

Go to the game-settings through the menu, Click the tail sticking out from behind the wet floor sign.

To get the Grandma, Earth, Mystical, Rock and Classique achievements you'll have to click on Fofinõ 3 times on that particular floor.

After finding Fifiño 3 times on every floor, they'll appear on floor #6 aka the roof, click to get the Found! achievement.
To get the Adopted achievement you'll have eto make the right choice by not being heartless.