Analyze the fundamental differences between two approaches for developing natural language processing solutions. The first approach involves training a unique, specialized model from scratch for each specific task (e.g., one model for sentiment analysis, another for translation). The second approach utilizes a single, large, pre-trained foundation model that can be guided to perform many different tasks by providing it with specific instructions at the time of use. In your analysis, compare these two approaches in terms of development time, required expertise, and overall system flexibility.