Regarding encryption of cells and formula
Recently I have created an excel file in which some of the cells are locked and hidden as those cells contains a logical formula that I don't want to show to others. It is working fine with every application across the Mobile and desktop including 3rd party application like WPS also. But when I opened it through "SHEET" - an android application then every cell which is locked and hidden as well as password-protected is now editable through SHEET application. So please look into this.
I have bad news my friend... there is no actual encryption at all. There is information that the file is meant to be regarded as encrypted and Excel will honor that requiring passwords and not allowing access as appropriate, but no company in the world has to do this. Anyone at all can simply open the file and see any content.
Only programs that simply honor the idea will not do so. It is all plain-text so... anything at all can read it, always. Some things just choose not to, to honor the idea.
So it's a major thing as they'd have to actually implement real (like not decipherable by a simple macro) encryption of the file contents. No encryption, no actual protection.
I myself use a macro from around 2002, freely available on the internet, that removes ALL internal protection and presents you two possibilities for the password the author used. That last is so that you may close and re-open the file, use one or the other password to relieve protections, do your work, then re-apply them as if they'd been in place always hoping to deceive someone about the fact you did things they wanted to prevent. For a moderate spreadsheet, three pages, it takes 2-3 seconds. (Pages matters more than number of cells in use for time.) The straw that broke my camel's back was a bank form that displayed (AND used) values in thousands (so "12" not "12,000") but had three mistakes with that which made the results wrong, and in my case, not in a way that was helpful! Just not having that.
Sheets has NEVER honored Excel's protections, ever. I believe, personally, that is a passive-aggressive dig at MS. Gotta trash the competitor however you can, I guess.
Very helpful if you ever want an unlocked view of an entire spreadsheet.
By the way, Adobe's PDF format has the same issue. Nothing is actually done to a file, just a few settings changes, which any other program is welcome to simply ignore. Don't want to take a form from the IRS and keep the several pages of cr*p they include, just want the form? Use something not Adobe to open it and delete the pages of chaff. Save, then use normally. Slightly more complicated than that, for the program doing it, but that's it.
Excel and PDF's are the two most prominent programs with this issue, but almost no one uses actual encryption at the equivalent of Excel's cell-level. Not even databases that advertise they do. Oh, and for Americans, there are no "4G" service towers in the US, no matter how many years you've heard of having 4G service. Curious to see if they are going to do the same with what will be called "5G"... all still 3G in truth. Liars. Scummy liars.
Good luck man. Got my vote.