>>714312450
TGAA is basically a spin-off (same gameplay, different aesthetic) so you don't have to worry about getting spoiled for the other ones. The games take place years before the main series.
>>714312691
Yes, that's true. My order recommendation was based on how played them (back to back while following release order). You can play the Investigations games first if those look more interesting, then do the Apollo games. That honestly might be more practical.