No, custom instructions stay with you and cannot be shared. What you can share is an agent, and only within your own organisation. When someone uses your agent, both sets of instructions apply: their own custom instructions and the instructions built into the agent.
More in Prompting Tips
Can I paste text into an AI Chat instead of uploading the file?
Yes, it is completely fine, but put the instruction first and the text after it. Pasting works perfectly for plain text such as a transcript or notes. For large files it is slower, and you lose images, charts and table structure, so uploading the file is better for those.
Can AI write a better Prompt for me?
Yes, and it is the preferred way to work. Ask the chatbot to write the prompt and give it as much information as possible: the scope, what to focus on, whether to search the web and whether to cite sources. AI explains a task to itself better than most people do. Check the prompt before you run it.
What is one-shot Prompting?
One-shot prompting means giving the chatbot one example of what you want. Zero-shot is no example and few-shot is several. The example shows the format, tone and length you expect, so the output matches it. It has nothing to do with shorter answers, the example sets whatever style you want.