Assuming your Hours and Minutes columns are of number type.
Try Using below formula:
=IF(AND([Hours]<24, [Minutes]<60); CONCATENATE([Hours], ":", [Minutes]); "23:59:59")
Sometimes comma(,) does not work in formula (I am not sure but it is based on something language or regional settings on your site). So in that case use semicolon(;) instead ...
Please check whether you check in, publish and approve the picture that you want to load on the page.
Did you modify the format of the picture before uploading it? Modify the format of picture may damage the picture. Try to change picture extension to PNG then upload the picture again.
And you could try to upload the pictures to the picture library first, ...
I would drop FBA and instead do AD FS & WAP w/ a non-claims aware relying party. This will allow you to use FBA (WAP) and Windows pre-auth. Your 3rd party users will need Active Directory domain accounts.
There is no way to make the Destination Folder required.
If it is a normal page like newform.aspx, we could use js code to do this. However,the upload.aspx page is an application page. We cannot make any customzations in application page.
Please share more information to further troubleshoot the issue:
You said "i have a page where the users send email", How did you send email to the page?
Do you mean when send email, there already has users in from address and you want remove the users?