The ladies wanted to open a garden shed double door that had a padlock on it. So Thyme hit the latch, not the lock, and the case of the lock fell off of the curved bar. Very doubtful. A padlock won't fall apart so easily.
The boys are shown in class with their teacher Oakely. But when Oakley invites Rosemary and Laura to dinner, he mentions it's Saturday.
The roses that Rosemary plans to plant in the bed include Rambling Rector, which is a rambler or climber. A professional gardener would know that it is unsuitable for a large bed in the middle of a lawn as it needs a wall, hedge, or tree to climb on.