Why is my kitten not eating dry food and having loose motions?

Given that she gets loose stools with even a little Royal Canin, I would try a different food instead. Hill Science diet is great, as well as Purina ProPlan and Iams. If any of them give her loose stools even with switching slowly, then I would stick with the Whiskas only.

It is important That Pelly eat mostly kitten food. You can certainly supplement with meat/fish but make sure at least 75% of her daily food intake is kitten food. Whiskas is not the highest quality food but if it's your only option, then go for it. Purina, Iams, Eukanuba and Science Diet are all good brands if you can get them. Make sure Pelly is appropriately dewormed to make sure the parasites are not making him too skinny. I hope this helps.

Whiskas is not a good quality food, if you plan to change the food, which i think is a good idea, try to switch to a different brand such as Orijen, Acana or Taste of the wild. if this doesn't work try Royal Canin, most cats love it and it is still much better than Whiskas.

There are lots of Whiskas products so I can't find the specific feeding guidelines for your cat food. There is usually a feeding guideline written on the bag or box of food that you can follow based on their current weight. If you can find this information and still have feeding questions, post a new question or choose a Petco Pet Education Center, formerly Petcoach Consult to discuss it further. Whiskas food is fine for cat's that are healthy on it! I do prefer that cats be on wet food instead of dry food as the extra moisture and higher protein content are great for cat nutrition. You may consider switching to canned Whiskas. I usually feed my cats Fancy Feast because that is easily found at my local grocery store. In general, canned cat food comes in 2 can sizes: small and large. I generally recommend feeding 1 small can twice a day for normal sized cats. Since Zoli is still growing, she may not eat the entire can, but you can still offer it to her to eat.

Royal canin and hills both make wet kitten food in foil pouches and I have had good feedback on the palatability of both of these. Cats can be very fussy eaters and it is not always easy to 'insist' they eat what we try to give them and I would be most concerned that she is getting the right balance of nutrients for kittens to grow and develop and sufficient fluid intake

It is okay for Muezza to primarily eat canned food although you may want to consider switching to Royal Canin canned since it follows the WSAVA guidelines for pet foods. If you feed table foods you should make sure they make up less than 10% of her total diet. https://www.wsava.org/WSAVA/media/Arpita-and-Emma-editorial/Selecting-the-Best-Food-for-your-Pet.pdf

She looks like a healthy little kitten, so I think she's probably OK and just being picky. If possible, I would contact the former caregiver and see what they were feeding. Sometimes they reject food that they are not familiar with. If you've done that already, or it is not possible, then try to feed a few different foods. She is old enough that she can eat 100% kitten food, so you can buy a few different cans of food at the pet store. Fancy feast is always a favorite. Don't feed too much at one time though, or she could develop vomiting/diarrhea. They also stop eating sometimes when they are feeling sick. If you notice some eye or nose discharge, or anything else concerning, then you may need to get her to a vet for evaluation. I hope that helps.