Update without wifi ?

Yes, you need a computer (PC a or Mac) running iTunes or if the Mac is running Catalina or Big Sur, you use the Finder. See the first section of this support article.

Update your iPhone, iPad, or iPod touch - Apple Support

Ask a friend who owns a computer if you can use theirs or take it to an Apple store and they will let you use theirs.

Yes, through your computer.

You're welcome.