Which do you prefer - set 1 or 2? Are all four examples technically correct?
At 10.05am, Paul was acquitted.
At 10am, Paul was acquitted.
At 10:05 am, Paul was acquitted.
At 10 am, Paul was acquitted.
In other words, instead of 'a.m.'/'p.m.', can they be written as I've done it?
I'm not sure why you've put them in those two sets. I can't see a connection between them. Putting a space before "am" in Set 2 doesn't explain why you have used "10:05" instead of "10.05". I used to see the colon used quite regularly when I travelled to continental Europe. It was used, for example, on the departures board for the Eurostar trains and I saw it again recently at a train station in Spain. We don't often use the colon in standard BrE writing though.
I would write "At 10.05am, Paul was acquitted" and "At 10am, Paul was acquitted".
Remember - correct capitalisation, punctuation and spacing make posts much easier to read.
Thank you kindly, emsr2d2.