Numbers 1 and 2 are common. Not doublechecking an application for completeness is like having spelling errors on your resume. If a person looking for a job will not take the utmost care to fill in the application and doublecheck it, then how good a job can you expect them to do once hired? The company only has the application and interview to assess a person's competance.
A person who bounces from job to job is unlikely to stay very long. Everyone in this position will come in with a good story for why they have had so many jobs. Unfortunately, past employers usually won't disclose why you left so a prospective employer may not be able to confirm the explanation. Unless the employer is looking for short term employees, its a risk to train someone who is probably going to bail after a year.
Pay issues, number 3, is at the sole discretion of the employer. Whoever they hire may be pleased to receive the pay they offer, depending on their qualifications. If they can't attract a qualified person at the lower pay rate, then they may raise the offer.
Item 4 may be contrary to state law depending on the job classification. For an hourly employee, or low level salaried, the law may require pay for all work, including training.