You really picked the wrong booking company here.
Typically multi-city itineraries are booked as a single ticket, even if they are operated by different airlines. That's typically done between partner airlines and allows the trip to managed as a single unit. The only booking agency that deviates from that is kiwi.com
First you need to check whether this is a single ticket or not. Check your booking records for each flight and find the ticket number. It's typically a 13 digit number. Check whether it's the same ticket number for each leg or if there are different ones (for the same passenger).
One ticket number: then you are in reasonably good shape. Look at the first three digits of the ticket number and look up the airline here https://www.kwe.co.jp/en/useful-contents/code1 . That's the "marketing carrier" and that's the airline that owes you a refund. Look up the CoVid policies of these airlines. These policies may be DIFFERENT from the legal requirements. Most North American and European airlines are legally required to give you a full refund but they still refuse to do it since they need to preserve cash.
Two or more ticket numbers: That's a problem. KIWI can only get a refund for the cancelled ticket and if they have to cancel the whole trip, they would need to refund you the other tickets out of their own pocket. They will dig in their heels hard to avoid that.
What to do
Make sure you have done your research first and you understand how your itinerary is booked, who is responsible for a refund (Kiwi or airline) and make sure you have a clear goal
Contact KIWI with a game plan. Make sure you clearly iterate your goal. "I want a full cash refund", "I will not accept re-booking or vouchers", "you are legally required to provide a full refund" "the policy that you just stated violates local law and I will not accept it".
- Keep good records with exact date and time. Transcribe the phone calls as good as you can. Screen shot any on-line chat. Keep all e-mails safe in a single place.
If they give you a refund, than you are clear. If not, you need to try again (2-3 times) and ask to talk to a manager. If that still fails, your best shot is to initiate a charge back with your credit card company . The credit card company will want to see your attempts to resolve this with the merchant, hence the need for good record keeping.
What is my right here?
That depends a lot on the details: type of booking, which airlines, which countries. Local laws are very different all around the world. It's also not a super relevant question. Currently airlines and booking agents frequently violate the law since it's hard for a passenger to do something about it and cash in hand is more important to them than some future legal liability.
what is the chance of getting all money refunded?
Hard to tell without knowing all the details. The good news is that US and EU governments have come down hard on the airlines to issue refunds instead of vouchers so this has gotten better recently. The bad news is that booking agents like KIWI sit a in a bit of a grey area KIWI is also one of the least reputable players in this field.