One at a time:
Will be possible in the far future to use megascale engineering to
create an artificial hollow moon to give Earth a big moon in the sky
like in billion years ago? Since it would be hollow, it would not have
surface gravity (this is what people say), so tides would not be a
problem. Am I right?
Wrong! it would still have a gravitational field, and its intensity would depend on the total mass of the hollow moon: it would be weaker if you just had a big big big big balloon in the sky, but it would be there.
If Mars and Venus get terraformed, they could have large moons as
If you want large moons to be engineered into orbit, like so many Star Wars' Death Stars you're welcome to do so. In fact, I like the idea for Mars, since it's climatic stability would greatly benefit from a moon that helped keeping the planet's axis in place. But it'd have to be a full moon, not hollow.
Albedo is not about being bigger, it's about reflectivity. Just look at our own Moon. It's not 'apparently bigger' than it is. You can choose mirror foils to turn it in a sort of 'disco ball' orbiting in the sky. It would be reflecting a lot of light and appear brighter than our moon.