Keil studio problems faced ı below

I do not know from where are points 2 and 3, but point 1 is know issue and was already reported few times (don’t ask me why it got resolved). However it is only an intellisense issue, compilation and your program will not affected, you can ignore that.

From Keil Studio’s release note:

Version 1.5.21
Fixes
C++ language support fixed for some standard library functions in Mbed projects.

BR, Jan