Equal sign allignment

I have 3 problems:
When continuing an equation on a line below I cannot align the equals sign below the one above - I read in the help that I should use empty braces before the equals sign to centre-align but this doesn’t work and produces the left and right braces symbol on the output page!
When I try to change font there is only one font option available.
I am using libreoffice version 5 on the pc but am unable to use any version with Mac OS v10.6.8, is this correct and if so what is the oldest Mac op. System that is compatible with libreoffices?

Regarding the alignment issue refer this answer. Regarding MacOS 10.6, from memory you are restricted to v4.3 (in v4.4 the baseline was raised to MacOS 10.8). Available from the download archive.