I read somewhere that Android/Linux keeps programs in working memory after they close so that when they're opened later then they can be opened faster. Is this true? If it is not, is there a way to enable this option (such as autocopying programs to a ramdisk for execution)?
Not the program as it is executed in memory but the page cache keeps all the files (executable, libraries, and configuration files). Thus the time for the disk access may be saved on the second execution. But the dynamic linking has to be done again.
i've read recently about the Sticky Bit.
Source One [sorry]: programs are loaded after startup into memory
Source Two [sorry, german https://de.wikipedia.org/wiki/Sticky_Bit]: programs are kept in memory after exiting.
It also says, modern implementation don't support it (the functionality) any more, so check your distro!