Can I run the following on my crosser? XT rear and sora front with Tiagra crank and sora shifters.Or will my chain mash into my gears causing me to crash into a child?

Should be fine, Specialized used to run MTB rear mechs on tricross’s and a few touring bikes come with road sti’s and mtb rear mechs. As there is more availability (or was) for mtb mechs with extra clearance for 9 speed.

Just make sure you get you chain length right.

A few riders rode MTB rear mechs and cassettes at the Giro this year so they could keep their front rings the same size, seemed to work OK.

Before the advent of 2*10 a fair few MTB racers used road mech too.

I’ve got sora shifters and Deore rear mech on my tourer. I ‘think’ all 8/9 speed Shimano stuff (Sora/Tiagra/Deore etc. etc.) is compatible

I’m runnung an XT rear mech ,Tiagra front mech with an FSA Omega road triple chainset and bar end shifters – works spot on