The acceptance rate for any journal may change from month to month, depending on the number of papers in the submission system. Acceptance rates are size-dependent, so that a journal that receives a hundred papers will have a lower acceptance rate than one that receives half that number.
The mean timespan from submission to publication can vary from approximately 91 to 639 days (median timespan varies from 70 to 558 days). Some journals now offer accelerated publication for select biomedical journals to coordinate publishing schedule with conferences, drug approvals, and drug launches. However, the cost can be substantially higher than most article processing fees.
If your paper is rejected because it wasn't a good fit for that particular journal, but it was otherwise a great paper and that journal is part of a transfer network, the paper may be referred to another relevant journal with the same publisher. It is then your choice as the author to transfer your paper to the new journal, and if you go that route, the paper is typically automatically transferred to the new journal's submission system, along with any reviewer reports it may have received. Your paper may be subjected to further editorial and peer review to determine if it is indeed a good for the new journal.
Typically, you can find information about the journal transfer system by googling the name and "journal transfer system" (or "article transfer system").
There are resources to help familiarize yourself with the process, its standards, and participating journals. Journals that participate are encouraged to adhere to standards set out by the National Information Standards Organization in the Transfer Code of Practice, so that the article transferred remains accessible and the process is smooth. Further, the Transfer Alert Service allows you to search for journal transfers, stayed informed on journal transfers via an RSS feed and sign-up mailing list, and a "query or integrate with the TAS" option via an API.
Again, a Google search of a journal and a publisher like Elsevier or Nature Portfolio will return information on their article transfer policies.