Depends on the model size. A model like GPT3 that has hundreds of billions of paramaters, you can do few-shot learning with. You'll still pay for the tokens processed and it'll at least linearly increase response times the larger your input is.
Fine-tuning can get you similar results on smaller / faster models. The downside is you have to craft the dataset in the right way. There are trade-offs to both approaches but fwiw, I don't think Alpaca-7b can do few-shot learning.
Almost. If your dataset contains questions and answers about your own projects documentation, then yes. The UX around how to prompt a fine-tuned model depends on the format of the dataset it's trained on.
One way you can do this is pass your documentation to a larger model (like a GPT3.5 / OSS equivalent) and have it generate the questions/answers. You can then use that dataset to fine-tune something like Llama to get conversation / relevant answers.