My previous advisor published a paper with my work and did not include me as a coauthor or give an acknowledgement. How to continue?
Contact the editor responsible. Talk nicely to him, and ask him how to proceed.

Since a friend of yours is included as coauthor without his knowledge,  you have quite some leeway. If one of the authors asks for the paper to be withdrawn because of incorrect attribution, this may very well happen. Such behavior is considered scientific misconduct.

Also many universities will have an office responsible for processing with plagiarism and other scientific misconduct, and may be able to assist you with drafting such emails.