Here are answers to your questions

Yes, the dog can lose weight during long boarding.
Reasons- Because of stress, the dog may eat less or skip meal Because of higher activity, if the dog does eat more than usual.
To address this issue- We always advise the parents to bring the dog to daycare / boarding a couple of times before the actual long-boarding . When the dog becomes familiar with the atmosphere, people, other dogs and routine…. Specifically after coming for a couple of times , the dog understands- he is going to go back to his family. After they develop this trust- normally the issue of losing weight gets addressed.
Secondly- we have a process of - weekly weight update for every dog that stays more than 1 week. We take the weight at the time of check in. Then every week, the parents get updates on weight and feeding charts. If we find the dog is losing weight- we discuss with the parents on what measures can be taken - like adding wet/ canned food or boiled meat to address the issue.

When the dog checks in for boarding, the customer fills up a form where they mention the frequency and amount of the dog’s daily meal every day. We follow the instructions during boarding. 
During long-boarding if we find the dog is losing weight, we discuss with the parent- if we can increase the food quantity or we can add canned / wet food or cooked meat.

Normally the moment we find out that a dog is on heat , we totally separate the dog from male/ not- neutered dogs. The fertile time of a female dog starts normally on the 4th / 5th day from the 1st day of her heat. So in a normal scenario, we spot a dog on heat much before her fertile period starts.
But still there can never be a 100% guarantee that pregnancy will happen- if by accident the dog gets mated by an intact male dog before we spot that, the dog is on heat.

Yes the dog can have common infections during their stay.
The vaccinations are given for -

• Rabies
• Distemper
• Hepatitis
• Parvo
• Lepto
• Kennel Cough

These are the main dangerous infections. All our dogs are not only fully vaccinated. But they are vacci/checked. Means - their immunity is also tested against those aforesaid infections. So the chances of dogs getting infected by dangerous diseases are almost none.
But there many common infections like- Giardia - It’s the most common diarrhea. A dog can carry this infection without showing any symptoms like diarrhea or vomiting. And just by sniffing the carrier dog’s poop in butt - other dogs can catch the infection. It all depends on the dog’s immunity.
Kennel- Cough ( KC ) - This vaccine is effective around 60% . So KC given dogs , staying with all KC given dogs - still can have this infection. But KC is a normal canine flu. For adult dogs - it's nothing to be scared of.
Conjunctivitis- This eye infection is in the air. The dog can have it from the atmosphere.
Hotspot- It's a skin issue. But it's not contagious. If the body immunity can not fight the bacteria on the skin - then this can appear.
Colitis - This gastrointestinal infection dog can get from atmosphere
We have 24/7 three vet support. So anytime we notice any unusual symptoms, we communicate with the parents and take veterinary help if required.
Our regular dogs who come weekly basis , we never had any infection issues with them. Because of their regular exposure in the daycare/ boarding, their immunity grows really well. So to address the issue of any kind of common infectious- dog’s immunity development is most important

Our supervisors have been working for us for 7+ years. They know each of our dogs. Our handlers have been working with us since a long time ( 2-3 years minimum), they are extremely experienced and more importantly they know each of the dogs. So any kind of argument / disagreement among dogs gets stopped before it even starts.
But still in the animal world- there can always be a moment even the best behaved dog may snap. But we are always here to make sure nothing serious must not happen. And we never mix up different sizes - so that no serious injuries can take place.

Yes - dogs will sleep long hours after going home. For 2-3 days we always advise-

• No change of food or no treat - this may cause diarrhea.
• Less food - this helps them to settle down faster & better.
• ⁠Only small walks. Long walks are normally not required.

After 2-3 days they all go back to their normal attitude.

After long boarding normally this doesn’t happen. All dogs have access to fresh clean water 24/7.
But the new dogs- after daycare or 1-2 nights boarding, drink lots of water after going home. Because of the new place, stress & separation anxiety, they don't want to share the water bowl. Though they have water available all the time. But once they settle down - this issue gets resolved. They start sharing water with their friends. We use only filtered water for our dogs.