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A: Usually, contaminated beers do not give favorable results. Exceptions occur rarely from wild contamination. If the contamination was from a cultured ''Brettanomyces'' that originated from equipment that was previously used for purposefully mixed fermentations, then the contaminated beer might turn out well because cultures from yeast labs are selected for their positive results. Otherwise, the chances of a wild contamination turning out good are very low. The best advice is to smell a sample of the beer, and if it does not smell good then dump the batch and brew a sour/funky beer on purpose (if the fermentation produces a fair amount of alcohol, it can be safely tasted after a month. See [[Wild_Yeast_Isolation#Safety|Safety]] for more information). If it smells good, the beer might be fine to package, however, even then your equipment will be exposed to the contaminating microbe(s) and there is no guarantee that the beer will continue to taste ok as it ages. Some contaminating microbes will slowly continue fermenting sugars in the beer and cause over-carbonation, bottle bombs, and increased off-flavors. So, the most pragmatic advice is to just dump it. If you choose to package the beer, keep the package cold so that the continued effects of the contamination are slowed as much as possible. Since the cost and time investments of a yeast starter/slurry are fairly low, it's best to just throw these out if they become infected and start over.
If you have space and time and want to simply learn what will happen with accidentally contaminated beer, then feel free to keep the beer in the fermenter and see how it evolves. Optionally, you could pitch Roeselare or some other [[Mixed_Cultures|mixed culture]] or [[Brettanomyces|Brett]] culture and see how it turns out after a few months. Brett can clean up some off flavors like diacetyl and acetaldehyde, but other off-flavors often won't be cleaned up by the Brett (like medicinal flavors and vomit/bile flavors). However, in the experience of most experienced sour beer brewers, this is not an efficient use of fermentation space. We recommend not wasting your time/fermentation space with accidental infections that show signs of off-flavors. Instead, use that space to brew an intentionally sour/funky beer and increase your chances of success.
As far as knowing what infected the beer based on what a pellicle looks like, the short answer is that [[Pellicle#Pellicle_Appearance_as_a_Microbe_Identifying_Indicator|you cannot confidently identify contaminating microbes based on what a pellicle or other visual signs look like to the naked eye]]. Microscopy can identify microbes to some degree (genus level), but DNA analysis is needed for species-level identification.