This is about iCloud, so I’ve moved this to Help.
For Obsidian crashing, more info would be needed. But see the debugging steps to try and narrow that down. But if you find a reproducible bug, please follow the template for bug reports.
First, search the help docs and this forum. Maybe your question has been answered! The debugging steps can help, too.
For iCloud not keeping local files, there are several discussions about this in the forum if you search. There are some “optimize” settings you can turn off. I don’t know about iPhone personally. Search results for 'icloud optimize' - Obsidian Forum