What aren't all functions from Excel available in Google Sheets?

Often functions do exist in Google Sheets but in different formats, for instance one of the features that drove me crazy about Google Sheets was that you couldn't insert multiple rows at once. Except you actually can, it's just not in the menu. Instead you need to: 1) Highlight the number of rows you want to insert (either above or below where you want to insert). 2) E.g. highlight the first 2 rows if you want to insert 2 rows above them. 3) Right click on the rows and you'll see you now have a number of options including "Insert 2 Above" and "Insert 2 Below". You can't simply clone someone else's software and make yours identical. Equally it may be that some algorithms are paid for or licensed differently, which could cause some functions to be missing.