OK - haven't read the whole thread - so my apologies if the question has been answered - but a few things for you to take on board.
Any wins in puppy do not exclude you from other classes such as maiden, novice, tyro and debutante
However, if you take 1st in Junior or above - whether it be at Open or Championship show level
- One win will exclude you from Maiden
- three wins exclude you from Novice
- Five wins exclude you from Tyro
- A first at a CH show at anything above Puppy will exclude you from Debutante
When checking your eligibility for classes - always check the 'qualification' date on the schedule - increasingly as entries go online and those closing dates shorten, this has the capacity to get more complicated.
For example - the postal closing date for a show is 10th August - the qualification date for the show will be 3rd August - so if you won a Junior class on the 4th August - your dog would still be eligible for Maiden.
Online closing dates can often be a week or even two after the postal closing date - but at the present time, it's 7 days before the postal closing date dictates eligibility.
The above is very generic overview of eligibility structure - your breed may not typically have Maiden and Novice classes at CH shows (they do appear occasionally at Open shows - but not that often).
Once you get past the age related classes (i.e. puppy. junior, yearling) - then class eligibility tends to be all around Championship show wins - Undergraduate is 3 wins, or a CC, Graduate and Post Graduate are 4 wins or a CC, and Limit is 7 wins in Limit or 2 CCs and must not be a champion - again eligibility dates come into play, and it is not uncommon, particularly over the summer, to see dogs still in Limit after they've been made up to a SH CH / CH.
Any wins regardless of class at Limit shows do not affect your eligibility for any class at Open or Championship Level - Limit shows are an excellent starting ground for young dogs and inexperienced handlers - as are Companion shows - both are also great fun and whilst you may get some pet dogs entered, the quality of entries in both is pretty much on a par with Open and Championship shows
Don't be put off by the "members only" limited show - with most general shows - you can usually just sign up and pay for membership with your entry. Breed club limited shows (where they exist) will be slightly different, as usually, to join a breed club, you will need a proposer and seconder and processing can take a little while as it has to go to committee.
If you win Best of Breed or Best Puppy in Breed, you are entitled to withdraw from any AV classes - but you cannot (contrary to what some believe) withdraw from any breed classes if you win your class - if you don't go into the other classes, then you cannot challenge for BP or BOB if you withdraw as you will be classed as a beaten dog.
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As someone else said - I would give classes such as Open a wide berth - because your dog will be immature - as you continue to show you will get to know your breed better and what show entries are like - and also how your dog competes against others.
With my first show girl, I had a tendency to put her into Graduate and sometimes Open - and she started consistently winning Graduate classes - doing us out of being able to compete in Maiden and Novice at CH shows - I've managed to do the same with my youngest boy through winning Junior classes

hey ho!!!!
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Best of luck with the showing - do let us know how you get on.