Not necessarily - it just changes the nature of the problem which becomes how to get it finished. In recent crashes where boats were covered by this sort of contract they were completed by either the administrator or the successor who picked up the pieces.
You were being very reasonable, but the company may not be in a position to give you any security over their work in hand or to park your money in an account with your name on it.
You will only know if you ask.
That is what a bank guarantee is. Not aware of any independent insurance policy for deposits with boat builders, for exactly the same reason bank guarantees are difficult - too risky or impossible to assess the risk. Most insurance policies for deposits are through trade associations (think building, double glazing etc) are organised and premiums are paid by members. No such scheme exists for boat builders because the number of builders is small, the collective risk of failure is small so there is not a large base over which to spread the risk - the fundamental principle of insurance.
It works in situations like that because there is data that allows insurers to calculate the risk. This is simply not available for buying boats where there are so few boats bought and so few failures.
I understood that this was standard practice (though I can't remember where I read it) otherwise you could find yourself in the situation that the firm went bust on handover day, and the administrator would sell the boat that you financed but have no rights over? Just because a company hasn't gone bust before is no guarantee in volatile times.
I assume you mean Princess Yachts of Plymouth.
Only if the contract says so. I don't know what form of contract Princess uses, but from what the OP says suggests the payments are unsecured. I used to work for a semi custom builder of powerboats, many for the commercial and export market and most were sold under a contract where title passed in stages, although my boss would always like to avoid that for private buyers!