You can program an aux switch to do the things you mentioned. The User Guide describes how to do this and lists the various functions you can have the aux switch perform.   If you are only using a single aux switch (with only one button) then you must use the "T+R" aux switch setting. For example, to tap tempo on your aux switch you would assign "TAP" to "T+R" in the SYSTEM/AUX SWITCH menu.