According to Illustration 5 LPM4 mode, can the UART use SMCLK to receive a character?

According to Illustration 5 In LPM3 mode, can the UART use ACLK to receive a character?

According to Illustration 5 in LPM4 is the data in SRAM lost?

In Illustration 5, if the CPU needs to poll an input to see if a switch is pressed (like the Arduino mode), what is the lowest power mode that can be used?

MSP430 Low Power Modes Off All CPU Off Active DCO on DCO on 45HA LPMO Clocks Off 220 100nA LPM4 RAM/SFR retained Stand-by DCO off ACLK on 0.3HA LPM3 RTC function LCD driver See all LPMs... RAM/SFR retained Specific values vary by device. MSP430 Low Power Modes Off All CPU Off Active DCO on DCO on 45HA LPMO Clocks Off 220 100nA LPM4 RAM/SFR retained Stand-by DCO off ACLK on 0.3HA LPM3 RTC function LCD driver See all LPMs... RAM/SFR retained Specific values vary by device