Regarding Icarus Excel Firmware

[RKuken]

Hello,

I just received my Icarus Excel. I'm excited about it.
However, I had a few questions regarding the firmware for experienced Icarus owners, before I got my hands wet.

1) My firmware is 1.820130716 - Should I upgrade to the latest? If issues arise with the latest one, can I downgrade? The reason I'm concerned is, I don't want to "end-up" somewhere I can't go back from.

2) Read a few threads and people keep talking about 'SD-Card' - Upgrading SD using SD-Card and putting fonts on SD-Card. I don't have one. Is it mandatory to buy one? Or just a good-idea to do so? What sort of SD card are we talking here? Any specific or will anything off amazon work.

3) Any best practices or do's and do not's - are most welcome.

Thanks